I've tried Smallworld and I can vouch that it is an awesome game! Like you said, it's kinda like Risk, but waaaay better!
Besides some imba race/power combos it's pretty well balanced. There are different maps depending on the number of players and the amount of race/power variations is big enough that almost every game is unique and different from the last.
Don't get me started on Smallworld Underworld and the various expansion packs... with that included you would need dozens and dozens of games to go through all the combinations.
tl;dr
It's an awesome game! I give ALL the thumbs up