Hrm. I like exploration to the extent that there's something interesting to see when you explore and the game doesn't seem to punish you for doing so. Back in days of yore, Daggerfall (you, know, that game before Morrowind?) bragged that it had twice as much land mass as Great Britain to explore, but a lot of it was a pain in the neck to get through (particularly mountains, given the semi-broken climbing mechanic), much of it was dull and "samey", and all of it was delightfully likely to get you randomly attacked for having the audacity not to use Fast Travel.
Games that genuinely make exploration rewarding require two things game developers tend to hate: creating interesting content that a significant portion of the audience will never see, and not forcing the player to actively engage every x minutes (usually through conflict) but rather take things at their own pace and thus risk the possibility that part of the audience may get bored and put the whole thing aside. Until someone comes up with a clever way around these two factors, I suspect mainstream games that make exploration for exploration's sake feel rewarding are going to remain a tiny minority.