WOW really doesn't take any skill. It just requires tons and tons of invested time leveling your character and completing missions. I mean don't get me wrong, I love MMORPG's but the best games, which are few to none, focus on skill rather than who's been playing the longest or who has the highest level, most gold, best weapons etc etc...
Guild Wars is great; tough to get into, but it provides an excellent opportunity to match skill against skill. EVE online is very very complex but it def requires skill in order to prevail. The Battlefield games require skill, provided you aren't using hacks or mods. Command and Conquer and Starcraft type RTS games also require skill and strategy to win.
Often you'll hear WOW players or similar MMORPG game players flame the games that require skill just because of that fact.
As for Second Life, this shouldn't even be a debate; SL isn't even a game it can be considered more of a virtual world.