Arkose: Mount&Blade is nothing like Oblivion, and in fact it came out long before it. It has brilliantly interactive combat system that is based on player skill as well as character skill. Horses are a central component of the game (hence the name), and it has the best implementation of mounted combat
ever. Be sure to try the demo.
I remember playing a beta of Mount&Blade, and yeah it did come out before Oblivion. In fact I think I played it because I was waiting for the latter to be released; but I was disappointed, so I went back to Mount. In fact, Dark Corners was overlooked because it was released (I think) on the same day as Oblivion from Bethesda. Seems crazy that they pretty much crippled their own release.
The one game I would recommend is
Dwarf Fortress which has a style reminiscent of MUDs, Rogue or Nethack. Be careful though, it is literally a world into which you can fall and never return from. If you want some idea of what the hell you're meant to do,
read this in-depth tutorial. I love this style of game, its awesome.