World of Warcraft: Burning Crusade
WHY?
*You've hit that wall known as Level 60, at least once if not multiple times, as WoW has been voted "Easiest MMO to Cap Out Ever"; Blizzard's new level cap of 70 will at least give you something higher to shoot for.
*They're not just upgrading spells and skills (like Conjure Water rank 32, or Kidney Shot rank 19); they're adding brand-new ones, as well as additional tiers in the talent trees.
*The socketed item phenomenon that was sort of "coined" by Diablo will be implemented and Jewelcrafting added to the tradesperson skill set.
*Alliance players will enjoy playing as Draenei, and the new Blood Elf race gives the Horde faction its first exercise in what humans perceive as sex appeal (even though those Troll females are pretty cute).
*If you're bored with the same old continents and dungeons--which you probably are--Burning Crusade adds the planet of Outland, formerly Draenor, around which Level 70 characters can fly on Nether Dragon mounts.
WHY NOT?
*You can't fight on your Nether Dragon, nor use it outside of Outland, and it's slower than the current flying contingent of Griffons and Bats.
*They're not planning to add new classes at this juncture, nor will the "hero class" be ready to launch.
*Those of you who've spent the last several hundred game hours getting those epic armor sets and Arathi stuff might be disappointed that they won't be the end-all and be-all anymore.
*And will the current zones all of a sudden become deserted when people flock to the new areas? (Have you been to the n00b zones in EverQuest in the past thousand years? The NPCs are there, but they're awfully lonely.)