Need advice of the MMO world.

I am a long(long) time online gamer. Predominantly I play FPS, but they are getting old. I have quite a lot of experience in the MMORPG world aswell. Most notably I played Ultima Online for 11 years, on and off. I also played Shadowbane, Anarchy Online, Silk Road Online, Runescape(lol), Well of Souls, and the list goes on and on.

So what I need your advice for is to find a game with rich PvP and deep structural elements. Ie. Shadowbane's Nation/Clan system wit hthe town siege was excellent. I want a game with massive group pvp and clan wars, but also with good 1v1 combat.

Serious suggestions only, please.

Thanks in advance.

PS, please don't suggest a game that is failing, or WoW. I tried it and it wasn't my cup of tea.

Have you tried warhammer? I guess it's the only game with strategic PvP until Aion comes out.
Besides those, there aren't any games with deep pvp out there, unfortunately.
RF Online has intense PvP, tho. If you are into skill based PvP you should try out Dungeon & Fighter or Lunia.

There is a MMO request section, try there. You could also look at the big game list / screenshot thread in the free MMO section.