I came across a blog entitled,
Flawless Victory: Why Fighting Games Take the Most Skill, on WoW Riot and I found it to be a fun read. Aside from it being the usual pointless internet endeavor to claim X is better than Y, it brings up some valid and interesting points, with a conclusion of:
Simply put, the most mediocre fighting game player has more skill than the best MMORPG player...
Mostly, the article details the stupidity of your average MMO / WoW player who thinks that they just ooze skill from every orifice. Especially in today's WoW where "skill" essentially translates to whether or not you are a Deathknight, Paladin, or Hunter.
The validity of the claim isn't limited to the present, though. Even when WoW was good, your best WoW players are still retards by comparison to average people who play fighters. And shooters too, for that matter--the pre-Source Counter Strike got somewhat close, but I don't think any other shooter has ever done that. In my opinion, no other genre can really compete, though I have heard some good arguments in favor of your best RTS's like pro-level Star Craft.

Why Fighting Games Take the Most Skill / SF4 and SSBB Thoughts
In addition, since I've had some time to play it now, here are my thoughts on Street Fighter 4.
While I don't think that SF4 beats out Super Smash Brothers Brawl, it is still a very, very good game. I certainly feel that in SF4, the player has less options, if not simply because of the traditional health bar system, versus SSBB's directionally influenced "king of the hill-style" system. But, despite the fact that SF4 is a very linear and traditional fighter, it's definitely very fun, very competitive, and very well made.
Overall, it feels great. Like Street Fighter 2 with more options and better graphics. The gameplay is well balanced, but it certainly favors offensive over defensive play. While there are a lot of options to help you out in situations where you feel pressured, there are even more that help you keep the opponent under pressure. This of course means that the game is more offensively oriented than SSBB, but what fighting game isn't?
The aggressive play style also makes the game feel less tactical, but not by a large margin. That's how Street Fighter is
supposed to feel, anyway.
The biggest reason I will continue to play SF4 is not the gameplay, though, it's the online play.
In Smash Brawl, the online play is terrible due to the technical limitations effected by the design of the game. This doesn't mean Nintendo is lazy; the problem is that in Smash, there are too many options. Let's take jumping, for instance; you have a range of 1 to 100 degrees or so that you can "float" around after you jump, combined with short hops, full hops, double jumps, and recoveries of different distances, arcs, and speeds. All of this means it is nearly impossible to program any sort of lag-reducing netcode, and without that, game's with just about anyone but your next door neighbor are laggy and neigh unplayable. Personally, I don't mind though, as I enjoy traveling and going to SSBB tournaments.
With Street Fighter 4, the online play is--from a technical standpoint-- more like a first person shooter. There is no directional influence. When you jump, you always go the same distance. You can jump up, forward, or back. Your kicks have the same affect each time they hit the opponent, rather than sending the enemy farther and farther away at various percentages, as in SSBB. This makes it very easy to netcode the game.
While SF4's lobby system is terrible and prone to disconnects (often booting me from games before they start), the actual matches are perfectly smooth about 90% of the time. This level of online playability will keep me playing SF4 in my freetime for quite a while.
In the end, SF4 is a great game and certainly the best tradional fighter on the market today. It won't take away Brawl's #1 spot in my heart, but either way, whether it's SF4 or SSBB, you can't disagree that when it comes to skill, there is nothing better than a fighting game.