These two replaced TO for me a while ago but I'll throw them in the mix as nobody else mentioned them:
Dragonica/Dragon Saga. Same cute manga-style graphics as TO, but sidescrolling action. It's a bit of a grind at higher levels, and even more pay to win than TO, but if you aren't really serious about winning PvP but want to have a fun it's a great game.
Lord of the Rings Online (LotRO). One of the mainstream MMOs, I was drawn to it cos I like the books, but in many respects it plays similar to TO, being based on moving around and using skill sets to attack enemies rather than action. There's a huge community and plenty of group instance dungeons or you can solo the whole thing through questing/grinding. Though visually it's very different to TO I would recommend trying LotRO out if you're looking for a long-term replacement; there's plenty on there to keep you occupied.
Lv. 22x SM; lv. 25x (mad) Scientist
Amatsubame, Lv. 68 Chaosmage
Lv. 85 Elf Loremaster