FreeCol

The old Civilization is probably my all-time favorite game, so FreeCol has a lot to live up to.

It does a very good job, however. The gameplay is very much like the original game.
Unit graphics are really well-made - the terrain graphics are rather bland.

There are still a lot of issues in 0.7.1. The king is a bit overzealous with taxes, and I've yet to conquer a city - I loose every attack, always.

The game is rather sluggish, even on my desktop machine (a Pentium 4, 1 GB RAM), most likely because the game is made in Java. It is playable, and enjoyable, though, even on my laptop, although there's a lot of downtime when changing turns.

The pathfinding algorithm still has problems with unexplored squares. It'll rather sail all the way around the world than pass an unexplored square.

All in all, this is a very well-made game, and around 100% feature complete.
Once the final issues are straightened out, it will be very enjoyable.