For me:
(1) Europe
Troll's is best. Issander's can be fun, but finding all the little 1 bonuses isn't easy. They aren't especially visible and searching for them is annoying. Ottaman's is great if you minimize the superbonuses; but I don't like version 1.1's appearance. Even though a lot of my ideas were used to make Major Risks' maps, I can't stand the two maps. Troll wouldn't let Major Risk publish a smaller, improved version of Europe ("Europe 2.0"), so it forced Major Risk to make much larger maps, which have the same bonus value system but across too much space. Every time I played the maps it felt like I was being punished. Maps that favor lots of clicking and spawning without too much strategic thought should be classified as a form of torture.
(2) Earth
I love the Small Earth map if playing Risk, but not on Warlight. Grundie's Earth map is annoying, especially in South America and Antarctica. Heavy Earth is a bit similar in that respect (too many damn territories in certain areas). Fizzer's "Modified" map is my favorite in this group.
(3) Roman Empire
Incaman's is the best example of cartography on Warlight. But it isn't as strategic as Vampire's. The bonus values of Incaman's are all the same. And for a map that size, it just becomes a big, messy game of growth. Vampire's is nice because of its smaller size, more strategic choke points, and more varied bonus values and sizes (which makes picking strategies part of the fun). Maps like Incaman's are annoying when picking. I prefer autodistribute for such maps, to avoid the pain of being forced to talk about and coordinate picks that don't really matter.
(4) Asia
I really like Texas John's map, though in real-time it can become a clicking race, given its size: whoever can click the fastest to get their turns in before the 5 minute real-time boot wins - or at least sometimes you feel this pressure, which takes away from the fun. But for multi-day games Texas' map is great. I have only played my Medium East Asia map once, but it was fun. I tried to make it a smaller, simpler version of Texas John's map, with strategic differences, so playing it would feel different from playing Texas John's. The China map has provided me with the most enjoyable games. My Asia map is ok, but is a bit dull in comparison to the first three: after playing the China map maybe 5 games in a row with Gnuff, Sze, Gangbang and a few others, we played a game on my Asia map and I was immediately disappointed by the change of pace. Eitz's map is great for 1v1s. I've never played Caio's map, because it's so big and has an odd appearance (like a misshapen fruit). I can't imagine how that could lead to short, sweet, strategic games, and think it'd instead lead to nasty, brutish, and long drawn-out games.
(5) Chaos' Fictional Islands
For his Battle Islands series, I like V most. It looks most realistic and it requires the most interesting strategies and tactics. I also enjoy his 4 Kingdoms map (
http://warlight.net/Map?ID=2899). The idea of competing kingdoms with more or less equal bonuses and equal access to each other is something that could be built upon.
(6) Big World
Caio's can be fun, but it is hard to play in real-time. It requires a lot of time clicking in orders. World Big isn't the most well made map. But if its appearance were cleaned up, it would be my favorite among this group of maps.