The best "exploration" games?

[noobish hat]

GNNNN! I still really want to play Exile, but I still don't have a BBC! Unlikely to find one here...

[VR46]

Or something a bit different, "Don't Starve", Google that and see if it appeals.

[Mayhem]

GNNNN! I still really want to play Exile, but I still don't have a BBC! Unlikely to find one here...

It was converted to C64 and Amiga three years later, so you have those options. The "in RAM" save state ability was excellent too, so you could quickly rewind and undo a mistake.

[MonkeyJuggleDX]

What's Just Cause 2 like for exploration?

Really good. The map is HUGE and most of it can be done in no set order.