Agree with this, never felt too empty when leveling a character, I think an area like The Barrens is always populated with people.
Barrens is, yes but more because at about level 18 most people realise they can't really be arsed levelling this character any further and go back to their mains
I've played WoW since open beta and recently lost interest after some unfortunate guild related drama involving my friends being unceremoniously kicked out and leaving me in a pain of a situation- obv I couldn't stay really.
WoW is really good. Especially if you're new to the genre. It's mechanics are simple enough that an intelligent chap or chapette can pick it up pretty quick and do a decent job of it, but deep enough that there is an enormous scope for min/maxing and trying to extract the best from your class. The PvP is fairly mediocre in my experience; the honour gear is easy enough to pick up, but then everyone has it meaning that battlegrounds are decked out in it and will dump on you for a good few weeks. The PvE though, in my experience was excellent. Even if you don't get in to high end guilds there's still a fair old bit to get stuck in to, and even more in WotLK by the looks of it.
WAR is also very good fun. The PvP is very satisfying, it's very well polished, especially for a new launch, and pretty well everything has been thought of. What's even better is people are still exploring, levelling, learning the mechanics and classes so you can kind of get in and run with it as it develops. Though my server's fairly dead, but pick a good one and I think you'll have a good time

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LOTRO was absolutely ******* awful. The graphics were poor, the quests and classes were boring and not terribly intuitive and I just generally got no 'feel' from it, it didn't spark me in any way. You're welcome to try though, your mileage may vary
Age of Conan most definitely wasn't any better, bug ridden, massively lacking in content and probably the worst interface and chat system I've seen in a game. I has high hopes and the graphics were fantastic but was woefully let down. It needed another 3 months development at least and now I suspect it's probably dead as everyone saw the state of the game and it lost about 65% of its playerbase.
EVE online was too much. The playerbase is too entrenched, the game is so ridiculously inconvenient and inaccessible that it's very very hard indeed for the newbie to get involved in any meaningful way. I sort of quite enjoyed my trial thingy and was considering subscribing thinking I was making some progress and then I encountered a couple of players who made me look like a gnat after 2 weeks of trying to work it out and realised the amount of time and effort I would have to put in and couldn't commit to it. The real time system seems silly to me too. I mean it's great in that it means that the players with the most spare time aren't always the most powerful but realistically they still will be.
I even tried Vanguard: Saga of Heroes for a bit. I say a bit. I mean less than one quest. It seemed really very bad.
The bottom line: War or WoW are probably you best bets imo. Good communities and solid games. LOTRO might work for you, it may not. Read and research. I also know nothing about Guild Wars or EQ2, but from what I've played WAR and WoW are the only ones still installed after the first week, let alone the free 28 day gametime.
No swearing