Stop talking about Bobby Fischer! Just stop, you'll be OK! Very few of us aRE Good enough to even have an opinion on your question.

Both Kasparov and Karpov at the peak of their careers are just amateurs in terms of their performance against their peers compared to Fischer. 

Neither Kasparov nor Karpov even had the ability to win a match against a top ranked contender with a score of 6-0 (against Larsen and Taimanov) and beating Petrosian in 9 games with a margin of 4 wins.

Neither of the two could have dominating performance against their peers as Fischer who finished Palma de Mallorca 3.5 points ahead of Larsen, Geller, Hubner Taimanov, Uhlmann, Portisch, etc.

The problem with having known Steinitz as a young man is losing touch with who Kasparov is.

He won the 1963–64 U.S. Championship 11–0, the only perfect score in the history of the tournament. In the early 1970s he became one of the most dominant players in modern history—winning the 1970 Interzonal by a record 3½-point margin and winning 20 consecutive games, including two unprecedented 6–0 sweeps in the Candidates Matches. According to research by Jeff Sonas, in 1971 Fischer had separated himself from the rest of the world by a larger margin of playing skill than any player since the 1870s  

Kasparov and Karpov could never have dominated a field the way Fischer dominated Palma de Mallorca? Kasparov and Karpov have won dozens of much stronger tournaments than that. To begin with Palma didn't have Spassky and Korchnoi, the two strongest Russian players. Fischer scored great results against the bottom half (but lost against Larsen). Fischer played four stronger tournaments in his career and didn't win any of them.

Kasparov rarely played in tournaments with so many weak opponents as Palma had (Jimenez, Rubinetti, Ujtumen, Naranja, Addison, Minic, Suttles, etc). Tilburg 1989 was a bit of an exception, where he too won with a margin of 3.5 points (in only 14 games instead of 23). The weakest player in the field was Piket, winner of Dortmund a few years later, all other participants were Candidates level. But this is just one of Kasparov's tournaments that rarely is noticed since he won so many stronger events for so many years, for example Linares 1999 with a margin of 2.5 points (14 games) ahead of Anand, Kramnik, Leko, Topalov, Ivanchuk, Adams and Svidler. All of the opponents being serious World Champion candidates.

Fischer's results against Taimanov and Larsen are often repeated, and one could just as well repeat that Steinitz won with a bigger score (7-0) against a much stronger opponent (world #2 Blackburne). Does that make Stenitz greater than Kasparov or Lasker? I don't think so, matches are a bit special. When Spassky played Larsen he too won his first three games, and then took it easy. Fischer himself said that his match against Taimanov just as well could have finished 3.5-2.5, but in matches the final result doesn't matter, it is only a question of winning or losing the match. As Larsen Taimanov threw away certain draws to try to win and it backfired. Anyway, beating Karpov time and again is always more impressive than beating Taimanov or Larsen, it doesn't have to do with match scores. Salov won a Candidates match 5-1 against Khalifman (later FIDE World Champion), and I wonder if anyone ever would mention that match if it had been 6-0 instead.

In the title match Fischer won 12.5-8.5 against Spassky, also there the result matters little, it was the same score Tal won with against Botvinnik. What mattered was that Fischer won and was the best player in the world in 1972. Since he wasn't interested in continuing playing it's hard to say how he would have fared against the stronger Karpov, who won 7-4 against Spassky in 1974. It would probably have been a tough match, but Fischer was at his peak and Karpov was still very young. At the same time Fischer hadn't played chess for years while Karpov was improving steadily.

Indeed Kasparov and Karpov in their time were at the top, the world's # 1. 

However, it needs to be pointed out that the record of these two champions are littered with draws against fellow GMs compared to Fischer. Indeed the tournament victories of both Kasparov and Karpov are most if not all littered with many draws. The number of draws that both Karpov and Kasparov were in the habit of making demonstrated that both were not as fierce a competitor as Bobby Fischer.

An Interzonal, like the 1970 Interzonal at Palma De Mallorca represents the cream of the GM and IM crop among the different zones in the world.  Spassky was not there because he was the defending champion.  Petrosian and Korchnoi were not there because they were seeded into the quarterfinals.

Against the 13 top GMs of his time (with Henrique Mecking, Vlastimil Hort and Boris Ivkov at the tail end of the 13) Fischer scored 9 wins (Geller, Taimanov, Uhlman, Smyslov, Gligoric, Panno, Mecking, Hort, and Ivkov) , 3 draws (Hubner, Portisch and polugayvesky)  and 1 loss (Larsen).  Overall, Fischer had 14 wins, 7 draws and 1 loss.

At Reggio Emilia (12/27/91 thru 1/06/92) one month before Kasparov's 29th birthday, the age when most chessplayers are at their peak, Kasparov played against 9 GMs and scored a measly 3 wins, drew against over half of the field (5 in all) and lost to one (to Anand).

Kasparov won the Tal Memorial PCA Super Classic in April 1995 with a score of 7.5, half a point ahead of Anand on 5 wins, 5 draws and no loss.

Kasparov also won the Lord Novgorod the Great PCA Super Classic in June 1995 with a score of 6.5, one point ahead of Ivanchuk on 4 wins and 5 draws.

In Budapest 1973, Karpov scored 3 wins and a pathetic 11 draws, one point behind Geller who had 6 wins and 9 draws.

However, Karpov did win Leningrad 1973 with 10 wins and 7 draws. Five of those wins were against IMs and 5 of those draws were against GMs.

In Hastings 1972, Karpov scored 8 wins, 6 draws and 1 loss against 5 GMs, 6 IMs, 2 untitled, and 2 unrated. Karpov drew against 4 GMs, lost to Korchnoi and drew against 3 IMs.

At 1972 San Antonio, Texas, USA, Karpov had 7 wins and 7 draws to tie for first at 10.5 with Portisch and Petrosian.

That in summary is why Fischer in his time stands taller than Karpov and Kasparov in their own time. 

By the way, neither Kasparov nor Karpov came even close to winning 10 straight much more approach Fischer's 20 straight wins.

Who the hell is Jeff Sonas?

Yep, Jeff is definitely not overrated! lol

Probably the guy who knows the most in the world about using advanced statistics to compare chess players...

http://www.chessmetrics.com/cm/

If not the top chess statistician then who else is?

lol...yeah well, whatever the heck that means... 

And Steinitz once won 25, so there... 

8 years

Well, speaking strictly from a chess rating perspective, check this out:

http://en.wikipedia.org/wiki/Methods_for_comparing_top_chess_players_throughout_history

It shows Garry Kasparov at 2851, first place and Magnus Carlsen at 2826, second place...with Bobby Fischer at 2785 at tenth place.

This info is not necessarily up to date. I think Carlsen is now higher, at the number one spot. I will go get that info and edit below.

Edited: Magnus Carlsen is now #1 at ................

Well, here is what I found: http://www.huffingtonpost.com/2010/01/04/magnus-carlsen-norwegian-_n_410853.html

That was at the end of his career I believe, his peak 1 year rating was actually the highest ever (2895), if you scroll down one paragraph from your quote you will see this.

Very well. Thank you.

I agree with this.  And I co-win.

I oppose you both earnestly and with vigour (more vigourous than America spelling.) I, therefore, take the prize from the both of you.