Guild Wars
Guild Wars has a big advantage because since there is no monthly fee, ArenaNet has no initiative to slow players down by having them level slow and filling them up with time sinks and money sinks so they will pay for more months of gameplay. Besides the challening PvE with fun engaging and truly hardcore AI, guild wars also have many large several hour epic missions that could either be done co-op or with henchmen. The beauty of this game is that you don't need a full party of real players to play, you can always flesh out your party with henchmen or heros if you have those campaigns.
My favorite thing about Guild Wars is that you can only carry 8 skills. In GW you might be an elementalist like me, but there are different types of elementalists. You choose all the skills that you have available between your 2 classes. So while being a certain class, you are actually a class within that class. While it's of no great importance on the gameplay, small things have always bugged me about this game, like invisible walls, the lack of a ability to swim or jump, no mounts, no way to have weapons on your back, no auction house.
