Melee was the best one
My thoughts:
N64: a nice change of pace sometimes that feels "organic" due to the controls so limited and original.
Melee: My first ever Super Smash Bros. game, so of course I'm nostalgic, but it is clear this is the fastest game by play speed. Ironic Brawl (next one) was the slowest of them all, so fastest to slowest felt REALLY slow in pace change.
Brawl: Sorry Brawl favorites; this has my vote as the worst Smash game (of the platform games listed/not counting side ones like 3DS) because of the super slow play speed and the ridiculous glitch tricks you are do to exploit this time. Even worse when you factor in some frame data tricks for crazy combos due to the slow game speed and button input times. Even though Brawl was my least favorite, the Sub space storymode was the best - I think we can all agree the teamwork of the characters and the story was unrivaled in the series
Wii U: Brawl super slow speed fixed and not as speedster as Melee; this game was a good balance and perhaps my go-to Smash game as of now.
Ultimate: I like the roster bringing all previous characters back and adding some. However, I can't critique Ultimate much, because I don't have a Nintendo Switch (I play Ultimate when a friend of our brings over their copy of the game on Switch). This might be the best Smash game as it is the most recent, but I can't fairly say due to only playing it a few times.
I really don't like how small the Switch controller(s) are though. Seriously, the buttons seem built for a 5 year old. My hands are probably about "average" size and I'm not clumsy, but the small button and controller(s) size is ridiculous; there should really be more controller compatibility than there is for this game.
Ngl, 64 is pretty cool for a start. In regards to gameplay, I think Melee is easily the best. It nails pretty much every aspect of the gameplay and is so much fun to play, especially considering it's a Gamecube game (I love that controller to death).
Brawl was my first Smash, and is probably my favourite for being the most enjoyable overall. In my book, as long as the game functions and you can still have fun with it, it doesn't have to have the most polished gameplay in the world. I have so much fun with Brawl because it feels appealing to me in comparison to all the others, and I find it to be the least boring. However, I respect your thoughts on it, and I completely understand where you're coming from in regards to it being the slowest. I'm glad we can agree it has the best single player, though, and I'd also say it has the best music in the series.
In regards to 4, for me it feels so much worse than Brawl despite having balanced speed. I felt that a lot of what captivated me with Brawl was gone, with an awful menu and generally worse aesthetic imo, as well as a worse single player, trophy collection minigame (which is an important part of it for me), and less of an incentive to play a lot of it. However, the Mii Fighters were a cool new addition, along with so many other new characters. A lot of the stages I thought were unique, although many of them felt too gimmicky for me, and Smash Run was still kinda enjoyable, even though it's nowhere nearly as good as its predecessors. Plus, the music was still pretty good.
Now we have Ultimate. I feel like my opinion may be controversial here, but I really think Ultimate is overrated. Don't get me wrong, it's still a great game, and I prefer it to 4 and the original, but I think it feels more like a throwback to the old stuff more than a fresh Smash Bros experience. While the speculation is cool, there was very few new characters in the base roster I was legitimately excited for, being Ridley, Simon, and King K Rool. I get that trophies would be kinda impractical at this point, but I do kinda miss them, as one of my favourite things to do in Smash was collect them. I find Spirits to be vastly inferior, especially considering I'm not really a fan of modifying characters before fighting, so they don't offer as much to me. And World Of Light is pretty bad imo. Like, I absolutely hate it. The DLC is pretty cool, and the game does an amazing job at building hype. But overall, I think it's kinda lackluster in comparison to previous games.
In regards to the controllers, I don't mind the Switch controllers, but if you want variety, the Gamecube controllers I'm pretty sure are compatible with the game if you use the Wii U Adapter. I think this may be the most controller compatible Smash Bros game because it's the only one to use a controller that wouldn't normally be used for that system
I wouldn't call 3DS a side one. I feel like 3DS and Wii U are two different aspects of the same game. It's as Sakurai described it. 3DS is the home, Wii U is the stadium
Yeah I know Wii U/3DS sort of go together, but they feel different to me since they literally have different stages (some are the same) and they feel like 2 different games to me with the 3DS one being an inferior shadow to the platform Wii U game.
I know this is just my perception and opinion, but the 3DS I didn't include; I was just commenting some loose thoughts on the 5 platform Smash games.