Play world of warcraft. I've been an avid WoW player for about 4 years, I played Aion for about 4 months and quit it. Aion has almost no endgame content, the player vs player (PVP) combat sucks. Aoin does have better character graphics, but a game with no content after leveling is just.....well down right boring.
WoW also has a larger player base and the game is just amazing in every aspect, leveling, professions, player vs player (PVP), player vs environemnt (PVE), etc etc
Play WoW and you want to play any other MMORPG (until SWTOR comes out)
WoW sucks sorry as it is too easy... Coming from Everquest then going to Age of Conan (terrible), to WoW i just found WoW to be very easy compared to EQ.
Maybe I am biased as I have been playing EQ since it was almost released and now play Shards of Dalaya which is like EQ but almost completely different.
If anyone wants a decent free MMO and doesnt care about old graphics then Shards of Dalaya is for you. Plenty of people there, plenty of quests, lots of stuff to do and they limited raids to only 18 people instead of EQ like you need 54.
Google Shards of Dalaya and you can see how it is.