Snake is better than Falco but worse than Diddy imo. If you're worried about renovation/freshness of his game, Havok has been doing a little bit of development for this character and doing fairly well. Results are still significantly stronger w/ snake than other characters barring MK. This thread pretty much debunks this "He's a one trick pony and hasn't won any significant earnings in awhile":
http://www.smashboards.com/showthread.php?t=295425&page=47 Falco gets hard countered by characters, which makes him just shy of being as solid as Snake and Diddy.
Also, Snake may get raped harder in situations, but he gets tons of life to do it and get it right. Anyone that doesn't have as amazing an offstage game as MK will still find it fairly difficult to keep snake away from resuming his strong ground game again. Not dying until 160% to most attacks at minimum makes for a lot of guesswork on the opponent's side, whereas Snake has much less a margin of error (as much as I hate that phrase).