For me I think one of the best is Capablancadue to the magnificence of his games. I would lke to state others that I think is included in one of the best lists but I won't since it is really subjective. We have preferences on how we say a player is the best and one of my basis is how beautifully they played chess.
Best Chess Player of all Time!

I know I suck, but at least I don't show off my games on YouTube.
Planet, let's get a couple of your games on Youtube!
I wouldn't want Magnus or Anand to see em, and get worried about the competition.

Is the Backyard Professor really 747? Is he really a person? See, I thought his videos showed obvious signs of being Fritz or Houdini, becaue no human could play like that! :-p
Seriously, though, what if his rating isn't correct? Perhaps he doesn't do rated games with USCF any more. Maybe he stopped before discovering his idol, IM Silman?

Kasparov. Thats it. Undisputed Best Chess PLayer ever live.
***Forum Rookie Alert***

"He who plays with Morphy must abandon all hope of catching him in a trap, no matter how cunningly laid, but must also know that it is so clear to Morphy that there's no question of a false step." -Adolf Anderssen

It all comes down to how one defines "best." There's good cases to be made for a whole host of players. If you value longevity at the top, there's Lasker, Korchnoi, Keres, Bronstein, Kasparov and Karpov to talk about. If you value winning percentages there's Fischer, Morphy, Capablanca and Alekhine. If you value tournament play there's Fischer, Karpov, Kasparov, Carlsen and Steinitz to name a few. If you value match play there's Steinitz again. If you value entertaining chess then Marshall, Rubenstein, and Tal might be your guys. If you value lasting contributions to theory then guys like Keres, Marshall, Kasparov, Nadjorf, Reti, Nimzovitch and others come to mind. If you value not losing over winning then Capablanca, Petrosian, Smyslov, Kramnik, . . . you get the idea.
What it all comes down to is that without specifically defined criteria and a methodology to compare players across eras the question basically just comes down to "what chess player do you subjectively like the best for their chess play on whatever unstated criteria you choose?"
And while it generates a ton of forum cruft, it is almost devoid of interest because it's just a bunch of largely unsubstantiated opinion.

Deep Houdini 3.
Also, and this opinion won't be popular, but I think Karpov would have defeated Fischer. Sure, he wouldn't clean him out, and the match would be somewhat close, but Karpov has amazing positional and defensive technique, and his pieces work in synergistic harmony. Fischer on the other hand, is a more aggressive attacking player. Sure he has a solid positional understanding, but Karpov was on another level in that area. I do like how Fischer could crack large pawn centers though, I still don't know why people still bother to put pawns on c4,d4,e4, and f4 given how broad centers can be cracked.
I just looked up his rating, and it's 747 USCF.