I disagree that after 1. e4 e5 2. Nf3 Nc6 3. c3 that d5 here gives Black a slight advantage.
What chess records may never be broken?

Certainly Fischer's consecutive win streak and Tal's two undefeated streaks (95 and 86, still the top two streaks ever, and against GM competition) seem unlikely to ever be broken.
And then Magnus broke the undefeated streak.

I disagree that after 1. e4 e5 2. Nf3 Nc6 3. c3 that d5 here gives Black a slight advantage.
It does, according to Stockfish. White's best move there is 4. Qa4, which is met by f6 and black still retains a slight advantage. The most obvious human move (and I assume the main book line) 4. exd5 is met by 4. Qxd5 (which I explained before, is better for black). 4. Bb5 can be met by dxe4 5. Nxe5 Qd5, which is also better for black. 4. d3 is too passive and can be met by 4. Nf6 or 4. dxe4, 5. dxe4 QxQ 6. KxQ and now white can't castle and his king is exposed. Both of those variations are better for black. What else you got?

3. c3 d5
4. Qa4 f6 i
5, d3 is close to equal for Black but White will strive to take advantage of Black's 4. .... f6 move.--I have won a few games this way.
3. c3 d5 4. Qa4 f6 and if White decides not to play the quiet variation it can get quite complicated but my 365 opening chess explorer White does better.
For your information 3. c3 d5 4. Bb5 simply loses for White--that is why it is correct to pl;ay
4. Qa4 for White,
By the way your evaluation of the line you gave after 4. Bg5 dxe4 is incorrect as shown by one of my games in the Finals of the USA Correspondence Chess Championship.
What you should realize that almost all normal openings--Ruy Lopez, Ponziani, Sicilianm 1. d4
1. c4
1. Nf3 these are all equal in the end and often whoever knows the opening theory best will have great chances to win. Thus my super record vs many strong masters and even a grandmaster!

3. c3 d5 4. Qa4 f6 5, d3 is close to equal for Black but White will strive to take advantage of Black's 4. .... f6 move.--I have won a few games this way.
That's not bad. Stockfish thinks that black is still slightly better or equal after 5. Be6 though.

The bust to the Ponziani Opening is 3. d5. Stockfish has this as being better for black. This is probably why we haven't seen the Ponziani played at the elite level for several decades.
It's on!
You take the black side of that. Ponz the white.
You can show Ponz how it is done!
I challenged Ponz to a daily game, a couple of years ago, and he made up some excuse why he couldn't play. Anyway, I'm a Sicilian player, so I haven't really studied that variation past move 4. I'm just saying that it's slightly better for black, according to Stockfish. Probably because there's a pawn on c3 where a knight should be, so after exd5 Qxd5, white can't gain a tempo with Nc3. Therefore, the Ponziani isn't as solid as the Ruy Lopez, Giuoco Piano, Scotch or Three Knights.
Well you dodged a bullet there, I tell you what.
I have seen this guy at work, and I have seen the way he analyzes.
I have spent a long time trying to find just one blunder in his analysis. And I am still looking.

I can't find it online, but It's mentioned in Murphy's history of chess: the slowest OTB game. Essentially some chess master decided he couldn't win a fair match against his opponent. (Circa 1880's to 1890's)
So he just took hours between moves, hoping his opponent would resign in disgust.
I'm thinking the game was against Paul Morphy, but I can't recollect who the player was that moved so slow.
Needless to say, chess clocks were invented shortly after that.
Paulsen?

I challenged Ponz to a daily game, a couple of years ago, and he made up some excuse why he couldn't play. Anyway, I'm a Sicilian player, so I haven't really studied that variation past move 4. I'm just saying that it's slightly better for black, according to Stockfish. Probably because there's a pawn on c3 where a knight should be, so after exd5 Qxd5, white can't gain a tempo with Nc3. Therefore, the Ponziani isn't as solid as the Ruy Lopez, Giuoco Piano, Scotch or Three Knights.
Well you dodged a bullet there, I tell you what.
I have seen this guy at work, and I have seen the way he analyzes.
I have spent a long time trying to find just one blunder in his analysis. And I am still looking.
I'm a pretty good daily player, myself. Anyway, he wouldn't be able to play the Ponziani against me, because I play the Sicilian. I'm also well-prepared for the Alapin's, if he chose to go that route.

I challenged Ponz to a daily game, a couple of years ago, and he made up some excuse why he couldn't play. Anyway, I'm a Sicilian player, so I haven't really studied that variation past move 4. I'm just saying that it's slightly better for black, according to Stockfish. Probably because there's a pawn on c3 where a knight should be, so after exd5 Qxd5, white can't gain a tempo with Nc3. Therefore, the Ponziani isn't as solid as the Ruy Lopez, Giuoco Piano, Scotch or Three Knights.
Well you dodged a bullet there, I tell you what.
I have seen this guy at work, and I have seen the way he analyzes.
I have spent a long time trying to find just one blunder in his analysis. And I am still looking.
I'm a pretty good daily player, myself. Anyway, he wouldn't be able to play the Ponziani against me, because I play the Sicilian. I'm also well-prepared for the Alapin's, if he chose to go that route.
His name is David Taylor.

Jeff I will remind you that in the Ruy Lopez White usually plays c3 so that your argument that White not being able to play Nc3 is moot.
One big advantage of the Ponziani is that the theory is about one tenth the theory of the Ruy Lopez. Not near so much to learn--but an experienced Ponziani player will have some advantages as shown in the game Where the 2nd best grand master in the world was losing in the opening against the Ponziani.
Also some of the analysis you gave was not correct so even someone trying to refute the Ponziani in public has problems.
I will also refer your to dozens of practical games shown in forums here.
The Ponziani is a good opening for players rated up to about 2350. I prefer 1. d4 myself.

Jeff I will remind you that in the Ruy Lopez White usually plays c3 so that your argument that White not being able to play Nc3 is moot.
One big advantage of the Ponziani is that the theory is about one tenth the theory of the Ruy Lopez. Not near so much to learn--but an experienced Ponziani player will have some advantages as shown in the game Where the 2nd best grand master in the world was losing in the opening against the Ponziani.
Also some of the analysis you gave was not correct so even someone trying to refute the Ponziani in public has problems.
I will also refer your to dozens of practical games shown in forums here.
The Ponziani is a good opening for players rated up to about 2350. I prefer 1. d4 myself.
I wasn't implying that c3 is a bad move in all openings. It's just too early to play it on move 3. That's why the Alapin's and Smith-Morra Gambit are somewhat dubious openings too, because c3 is played too soon. In the Ruy Lopez it is usually played around move 6, after white has castled and can protect the e pawn with his rook. In the Sicilian Rossolimo Attack, we can also see that the proper time and place to play c3 is after white castles and plays 5. Re1, to protect the e4 pawn. Now 6. c3 is a valid move because Nc3 is no longer needed to protect e4

Jeff, the fact that white has not 0-0ed before playing c3 plays almost no roll in the Ponziani as White has no need to play Re1 to protect his e pawn. so after 1. e4 e5 2. Nf3 Nc6 3. c3 Nf6 [attacking the e pawn] White has 4. d4! .

The Smith Morra is dubious because White sacrificed a pawn. The Sicilian Rossolimo is not very comparable to the Ponziani. [I play both with good results] Not sure what is "Alapin"?

The Smith Morra is dubious because White sacrificed a pawn. The Sicilian Rossolimo is not very comparable to the Ponziani. [I play both with good results] Not sure what is "Alapin"?
The Alapin is a variation of the Sicilian Defense, that is very similar to the Ponziani. It goes like this:

Jeff, the fact that white has not 0-0ed before playing c3 plays almost no roll in the Ponziani as White has no need to play Re1 to protect his e pawn. so after 1. e4 e5 2. Nf3 Nc6 3. c3 Nf6 [attacking the e pawn] White has 4. d4! .
That's why it's better for black to play 3. d5 (which stops white from playing d4-d5).

The Alapin is not similar to the Ponziani in the variation 1. e4 c5 2. c3 d5--the addition of Nf3 for White and Nc6 for Black makes all the difference in the world.
The variation with 1. e4 c5 2. Nf3 Nc6 3, c3 d5 4. exd5 Qxd5 is approximately equal.
However I play the following line [with very good results]
However in that line I play
Kasparov became the youngest at 22 to win the WCC by defeating Kasparov in 1985...
But if you play yourself it's usually easy to come away with a point.

The Alapin is not similar to the Ponziani in the variation 1. e4 c5 2. c3 d5--the addition of Nf3 for White and Nc6 for Black makes all the difference in the world.
The variation with 1. e4 c5 2. Nf3 Nc6 3, c3 d5 4. exd5 Qxd5 is approximately equal.
Well, the 2. c3 version of the Alapin is played a lot more often, but I don't agree that the inclusion of the knights makes all the difference in the world. The evaluations are relatively the same for both positions. 2. c3 d5 gives white a +0.50 score, while 2. Nf3 Nc6 3. c3 d5 gives white a +0.46 score. Also, exd5 is the best continuation for white in both variations. So, I don't see a whole lot of difference there. I agree that 2. Nf3 d6 3. c3 and 2. Nf3 e6 3. c3 are quite different though.
I can't find it online, but It's mentioned in Murphy's history of chess: the slowest OTB game. Essentially some chess master decided he couldn't win a fair match against his opponent. (Circa 1880's to 1890's)
So he just took hours between moves, hoping his opponent would resign in disgust.
I'm thinking the game was against Paul Morphy, but I can't recollect who the player was that moved so slow.
Needless to say, chess clocks were invented shortly after that.
That sounds like something I would have done. lol Not so my opponent would resign in disgust, but because I'm a perfectionist and a deep thinker and it takes me longer to calculate variations and find the best candidate move. I've actually had players sigh or tell me that I was taking too long to move, when I used to play OTB chess without a clock.