I just read up on Jeran Tek's epic trek across all of the EVE Online universe - yes, all 5000+ systems. A great achievement, for which he got a nomination for the E-ON Magazine Award 2009. I never quite realised how big this place really is! Here's the map of the entire EVE galaxy; the grey dots are systems I haven't been to yet. Still lots of room for exploration!
I can't imagine something like this in Second Life, though. In SL, the map changes continuously as islands are added or vacated; buyers change the names of the regions they just bought on a whim. But then, Second Life isn't intended for travel or exploration, even though there are some really nice places to explore.