When it's D&D4e!
OK, I'm being very specific here but 4e is raising very MMO-ish feelings in me.
1. There is a level of 'must play again'-ness rising in my mind. I want to see what happens next, not only in the game but also in the statistical development of the character.Optimising the choices that I make with each level is becoming an intricate process. Feats, Powers, Stats, Skills - its all very relevant and very enthralling for me on a certain level.
2. Builds! I've been running through different builds in my head and on paper and I have began to see different routes that a character could take. I realise now I have made a fundamental mistake with Morn, making his primary stat STR when it should have been CHA. However there are some great synergistic (is that even a word?) combinations of powers coming in the future. Its a lot of fun.
3. ALTS! Gah! One of the things that I have realised over the years is that we tend to play a game once. We rarely return to something we have already played. So this could be it for D&D4e! I only get to play a Paladin. But what about the Warlock? What about the Halfling 2H Weapon Ranger? What about the Eladrin Fighter? I want to make alts! I want to try new stuff out. Its almost tempting to seek a second group to try it out. (Tempting but inevitably flawed and deadly)
I can feel my MMO-senses tingling with 4e. The same feelings, the same thrill on levelling, the same development of powers and the same yearning to explore things from a different angle. Very clever.