I tried most of the maps. I vary map types in my games, though I prefer some over others.
Hemispheres - a very good map type. Customizable landmasses, good terrain.
Pangaea - The map I played almost exclusively for a long time. Now I rarely play it. The land is often badly balanced. Also having only one landmass makes the game easier. Still, a good map for a quick game with few opponents.
Big and Small - I only recently discovered this map. Feels very natural and interesting. You really need to have a navy on this one. That's one part of the game I've completely neglected until now.
Lakes - I like that a lot. Sure, it's all land war. But you have neighbors on all sides, sometimes as many as five civs have common borders with you. That makes for an extremely tense game - you have to expect an invasion at any time, from any direction.
Highlands - in fact I play it very rarely, but is has a certain appeal. Because the map is so impassable and wild there remains a large part unsettled for a long time which leads to massive barbarian uprisings. In a multiplayer game I played on this map we actually had to team up and help each other to not be destroyed by barbarians.
Maps I don't like:
Continents - the weak variant of Hemispheres, never liked it. Since Hemispheres is around there's really no reason at all to play Continents.
Fantasy - wildly mixed terrain, desert tile next to tundra tile, gems on ice etc. Sounds like fun, but isn't.
Terra - would be good if the AI knew how to handle it. As it is, the AI doesn't know the right approach to settle the New World, making the later game too easy.