it's not so much about replay factor but rather "keep me playing past lvl 60 and capped professions" factor=)
The reason people ask about longtivity, inspite of the fact there is no "end" to MMO's, can be summed up well by looking at the MMO: city of heroes, great concept, I for one loved the idea of being a superhero, reading comics as i have since i was able to look at pictures) i played that game to death the first 6 or so weeks, then it hit me, what was there to do that was different, it was grind, get level, at level you ether upgraded an existing skill by the amount of power-up slots it had, or gained a new skill of your choosing, other then this you could buy or loot(more random then anything else) the powerups to go into the slots for your skills and you could earn the right to a new costume at lvl 20, did i mention you could grind to the next level?
All in all a very tedious process im sure you'll agree, in fact the best thing about city of heroes was starting a new toon, the options avalible for your costume and shape was absolutly staggering, and every MMO around could do with taking a leaf from their book
I digress anyhow=) sorry, what i'm saying is that as well polished and original a game is, nothing beats gameplay and longtivity in most gamers eyes, another example, thou this one good is this, after well over 7 years, i still like to play final fantasy 7, in fact i've completed it from start to finish around 4-5 times now, i just love it, the combnations of matiera(sp) seemed endless, still a system i don't think has ben beaten by any other FF game imho, this game isn't even online, but something keeps me coming back once in a blue moon to re-live past glories!
Thats what EQ done in many ways, but it became ruined by varent/sol's attitude of creating timesinks after timesinks
I'm almost praying WoW will capture me like EQ, and to a lesser extent, FF7 did.
Majria
PS sorry to go on=)