I have been looking around and asking around for similar games for awhile too,and so far the only games I have come across that are similar are other Elder Scrolls games,and the Fallout series. Although if you really want to branch out,I would recommend playing other RPG games.
There are lots of great RPGs out there (Neverwinter Nights, Dragon's Age, Baldur's Gate, etc.). None of them are as open worlded as Elder Scrolls is but they are very good, though in a different way. If you aren't necessarily looking for an open world game I would try some of the other great RPGs that are available.