Love WoW and sofar has kept me playing because
1) Haven't finished the quests in the Human lands
2) Only just grazed the story in the Troll/Orc Hordish area, and just the tip of the quests and state of things there
3) Can barely mention the story of the undead and their realms.
4) Haven't tried classes beyond Alchemy, herbalism, skinning, tailoring, and leatherworking.
5) Haven't tried all the classes, and I perceive them as different despite balancing. Each have different roles and main home area's. Each have different styles of combat or focus of combat. Throw on either the Horde mentality or Alliance etc.
6) When trying something new you get alot of the enjoyment up front with alot of quests, a few morsels of the classes ability, and fun without having to work or feel a loss of not working on your other char.
7) Has the feel of WoW, my rts days
This is different to SWG which was mainly
1) STARWARS!!!!!!
2) er, Starwars... Plus had starwars stuff in it
3) what was then ok quests, didn't think there were better. Plus had alot to explore that just showed me more starwars. Environment was a big factor.
4) watching a character develop.
After playing both, I prefer the abundance and huge choice that WoW starts with at the beginning. Starwars started you with very little and a long journey ahead of you. I don't think I could go back. Or, at this stage switch to a game that has that quality. I kept playing though cause it was Starwars, a bit of an escape from the day.
I keep playing WoW because it is still a world to me to adventure in, while I have fun