@WoW, sure, some people can get hooked on any game. I'm sure there are some bejeweled addicts out there.
The point, and this is not personal experience but what I've gathered from several friends that played for years, is that WoW is only fun when you start playing it a lot.
There's no quick "jump into a match and have some fun" mode like other games have, unless hunting lvl 2-10 creatures is your idea of fun.
Considerable grinding/leveling is required to get anywhere in the game, as well as a network of guild members or people you can party with.
WoW being a stat-based game, your main objective will be to raise those stats. Seeing as it takes loads of time to even get near the level of some of the regular players, you're always going to be 'losing', even if it doesn't really have to be a contest.
Improving isn't a question of learning some tricks or changing a strategy, the way you would in an RTS or action game, it's a matter of grinding for a month.
If you can play it without the need to improve and enjoy the lower-tier gameplay of WoW, sure, go for it. Other than that, it won't be much fun.
OT:
Big freakin' yes for Morrowind. It's also an RPG, thus stats based, yet it's not an MMO. Because of this, combat and storyline are based on both stats and strategy/skill. Apart from a clunky melee system, this one is still at the top of my list for RPG's. I've played through it three times, each time with different classes and every time I've run into other difficulties and new quests that I didn't get the last time.
Thief 3, I think it was mentioned before, is great too. You should definitely have played this at least once, if only for some very memorable missions near the end of the game. Thief 2 is more solid, overall, but is quite dated and this might ruin the experience (because Thief games rely heavily on immersion and shadow effects)
As for RTS games, the old classic starcraft is great. Plus you'll be better prepared for when SCII comes around. It's hard to learn though, it'll take you a while before you can even take on the bots, let alone Koreans
An easier, more recent, but still fun game is Red Alert 3. RA3 matches are a lot more about choosing a build, scouting and combat than (recreational level) Starcraft is. In other words, you don't have to micromanage every freaking little thing
Furthermore, there's a difficulty setting for the bots which helps ..a lot. There's generally some strategies, especially for the Russians, that you can figure out within 2 hours of installing the game, that work fairly well against computer opponents, so you can get right into the game.
