I guess it's 7 survival maps plus 1 Chaos mode map:
My best solo - Wave 32 - 15,600 on the leaderboards, which is the top 1.05%
My best co-op - Wave 45 - 17,700 on leaderboards, which is the top 0.46%
My best solo - Wave 25 - 3,000 on the leaderboad, the top 0.32%
My best co-op - Wave 25 - 60,700 on the leaderboard, the top 2.4%
Bakaara mostly because of the memories. I played this map dozens of times split-screen with a good friend, just having fun. It's a real challenge.
Best solo - Wave 25 - 9,800 on the leaderboard, the top 0.99%
Best co-op - Wave 28 - 26,900 on the leaderboard, the top 1.09%
Piazza's many levels and verticality work really well, more so than Carbon which has a similar hillside design. I really enjoyed Piazza in a lot of game modes including survival. Plus it's just a great looking map.
Best solo - Wave 39 - 222 on leaderboard, the top 0.092%
Best co-op - Wave 27 - 35,400 on leaderboard, the top 8.86%
I bet you can guess part of the reason I like this map, it looks great. Bright, lots of color, but also it has an interesting layout that makes for good strategy.
Best co-op - Wave 38 - 1,200 on the leaderboard, the top 0.56%
Off Shore would have gotten a spot on the basis of it's singular wave progression, but it actually has a great setup with lots of levels, stairs and hallways. All of it together makes for interesting and fun gameplay.
Best solo - Wave 24 - 1,014 on the leaderboard, the top 1.04%
Best co-op - Wave 25 - 2,700 on the leaderboard, the top 1.64%
Parish is small and frantic, just like in multiplayer. It would look better if they took out some of the cloudiness though.
Best solo - Wave 29 - 136 on the leaderboard, the top 0.31%
Best co-op - Wave 19 - 10,800 on the leaderboard, the top 19.64%
Chaos mode is technically a sub-segment of survival mode and Dome is the most fun of the maps included in that mode. I still think they should have made Chaos mode for the Face Off maps, but oh well.
Best solo - 18.32 million - 328 combo - 4,400 on the leaderboard, the top 1.93%
No co-op score.
CoD4 and MW2 maps that I think would be a lot of fun in survival mode: