it the game as long and entertaining as Fallout 3 (BEST GAME EVER!!!), and does it have more variation in the world design than Oblivion?

The game is much smaller. It’s more varied than Oblivion because it doesn’t copy/paste content like Oblivion does, but it’s much more linear. A very different kind of experience.

also, does it rely on dungeons, or is it mostly above groung like the first. oh, n how similar is it to the first?

It has plenty of dungeons. At first they’re fun, but later in the game they get quite boring. At least they’re prettier than Oblivion’s dungeons. There is also some above-ground exploration, some of which is fun. The beginning of the game is much better than the later stages, though.

Divinity II very different from the first game. Some of the really good features from the first game are missing, and the sense of freedom is much smaller. On the other hand, I actually finished Divinity II, whereas the first one just became frustrating near the end and made me stop.

All in all, don’t expect a game similar to Oblivion or Fallout (or Divine Divinity). This is much more linear, and much smaller. It still has some truly fun features, though.