There was WoW. There is AoC. There will be Warhammer Online.
Any other games that came out since WoW that claimed to be direct competitors, weren't. So they don't count at all in this timeline. AoC doesn't seem to have taken the role as the next gen's mainstream mmorpg. So maybe it'll be WO. I don't know of anything else.
I bought Age of Conan. It was good for the short time that any decent game that puts you back $50 should. But that might've been altogether no more than a month of on and off play. Sales figures have broken records in multiple places, and supposedly 1 million copies have sold. But I really doubted the successes of Funcom's new high-budget mmorpg/WoW competitor. So I went looking on the internet to confirm my suspicions. I found that I am not alone. The following article is the best assesment of what might be going with AoC, and why it might be going on.
http://wowriot.gameriot.com/blogs/Epidemic-Obesity/Age-of-Conan-Desperate-for-Subscribers/ One personal thing that I've found, is that I can have TOO MANY quests. AoC throws tons of quests at you, so much that it's obvious that they thought, "The more, the better." This isn't true for me. It feels so disorganized, and it's hard to focus on any single task. Never thought it could happen myself, but too many quests = grind. I only reference WoW here because I have no other game worthy of comparison: WoW's progression of quests in Outland is a good amount. Enough to give you some choices, few enough to stay organized.
On a plus note, the graphics that the game boasted are absolutely amazing. But even I can't run them smoothly. The DirectX 10 client isn't even out yet. It will likely suffer 60-80% frames-per-second loss in performance. The extreme-performance pc gamer niche market (of which only a fraction wants to play MMORPGs) is much too small to support such a high-investment game. Note: Lowest settings in AoC do not perform any better with any amount of RAM (I have 6 gigs now, and the game still dragged like crazy at some lowest settings; ran best with certain settings maxed out).
Hopefully the Warhammer devs will take notice and confirm that their product isn't headed for any of the same pitfalls. What those pitfalls are, is still up to some debate.
I haven't gotten around to really reading about Warhammer Online (WO?), b/c it still seems a bit early to get excited about alpha/beta/whateva features. Looks like it will be a bit stylized and kooky(?) like WoW was/is -- AoC had great architectural design but (for perhaps obvious reasons) it's all based on real cultures and quickly gets boring, as good as it looks -- and since they're essentially the same types of universes (durr), the Lore should be pretty interesting too.
*update:
-RvR stuff looks interesting though I worry about the possible existence of underdogs (one side always winning, one side always losing). Also RvR always going on at the macro level: do you really care (everything you do is micro-level, miniscule in a world of thousands of players)? They haven't revealed anything yet about the rewards you will get for each part you do besides knowing that you contributed to the overall war effort ("You increased your side's Victory Points by 1! (1,362,164 to 1,362,165)"). I need a little more than that.
-PvP collision detection, such a disgusting mess for programming and latency issues, but getting between a squishiy and a slicey(?) will mean a hell of a lot more with collision detection. EVERY GAME OUT RIGHT NOW with collision detection suffers dreadfully with nearly any bump in latency. TF2 has the best motion prediction I've ever seen and it still suffers from jerking and jarring occasionally due to bumps in latency, but they did a really good job nonetheless.
-No dedicated healing classes/specs/whatevs, which is exactly what AoC did. Turns out I actually like healing :( Too bad for me. I played a Cleric in AoC, one of the classes capable of healing. It was alright. I imagine being surrounded by a wall of warriors would be pretty neat. Too bad I only leveled halfway up (40 of 80) before getting bored. Also to note, the levels felt meaningless as they came quickly and most of them didn't teach you anything new. Should completely do away with "leveling up" in mmorpgs (i.e. you have no level whatsoever).
As usual, none of these are judgements (the game isn't out), just observations that haven't had any answers yet, and likely won't until I actually play the game.