SSFIV is exactly as it should be, plus more fun.
People complaining about the outdated gameplay obviously dont know what they are saying. It DOES play just like every other SF, probably because it is a SF game. But as said, ultra combos are added, new characters, additional moves to some classic characters, and a very fluent mechanics system make it a new experience, while keeping the hardcore vibe intact.
The online play is incredible. Not much different from other fighters, but the achievements in it are challenging and fun to unlock, making you a better player every step of the way.
Some note that the graphics are a bit corny. Yes, this may be so, but the gameplay wouldn't connect with them as well if they were like, for example, Tekken. The actions would be slower and, in my opinion, the combos wouldn't look as brilliant and brutal.
If you like quick paced fighters, with a ton of classic characters and a mix of goofy and badass new characters added to the roster who have incredible new persona's and move sets, and beautiful stage graphics, then get this game, its a blast.
The only fault is I think they could have done a lot more with the enviroments. Remember the crates in Guile's stage in SFII? I know I do. Best example being 'Solar Eclipse'. Beatiful.