GW2 looks veeeeeeeery themeparkish to me. Also, their world PvP will most likely be RvR or FvF, which I don't like at all. GvG PvP will be the same instanced tournament crap that they have in GW. I really don't get the appeal of that, since if I wanna play 8v8 I'd rather play an FPS game.
Lineage 2 castle sieges were fun as well, largest I've seen were like 200vs200, largest I've been apart of was 80vs150. Yeah, I know, Korean grind game, but it was non instanced and FFA PvP (except for towns).