I think 'best game' is a broad thing to say since everyones preferences are different.

For instance, people who really like to get into games and totally immers themselves in a world without needing to Role Play might be better off with WoW.

But those deeply into fantasy, and roleplay as well as wanting an all immersing experience might like LOTRO. :)

My personal preference is Guild Wars, it's a one shot buy since the online play is free. Since I have little time to play it, the short quests and missions let me knock off one or two when I feel like playing, but I won't be shunned of ;'behind' anyone if I don't play for two weeks.

City Of Heroes is also a genre game, it's superheroes not typical fantasy and it's so much fun! I *adore* it. <3's the flying.