I have noticed after looking at the number of downloads on some maps/gametypes, that the map usualy gets a lot more downloads then the corresponding gametype. At first I assumed it's because the gametype was edited and re-uploaded, but I see it evreywhere. In the case of infection, a map is almost unplayable without the gametype to go with it. So I'm curious, why would you download a map that uses a custom gametype, without downloading a gametype? Example: Halo Wars game. Map: Over 3000 DL's Gametype: Only about 1300 DL's. NOTE: I am not advertising the Halo Wars map, I am simply using an example.
Halo 3 maps have seemed to unfortunately taken a bad path, similar to Farcry 2 which has an amazing map creator. Maps seem to be more of works of art now. People will download a cool map and show it to their friends just for the purpose of looking at it, not playing on it. I know I do that. People make maps with aesthetics in mind first, then gameplay because that is what gets you the downloads most of the time. Another idea to why this happens is because people check out a lot of maps. Maybe they download a map to check it out, and if they think it has a chance of playing good then they will get the gametype. If they think the map is hopeless after a look around, maybe they just forget about it and delete it. Another reason could be that a downloader does not know what gametype goes with the map they downloaded. I think the main reason is my first reason. Players just download maps because they look cool, or do something really unique; they never have any intention to ever play the map. I don't think Halo 3 is quite at Farcry 2's level though because you can't make maps that pretty, so you have to focus on gameplay more. Also, there are many more gametypes/minigames you can play in Halo 3 vs. Farcry 2, which keeps maps fresh. But Halo 3 will eventually get there. There will be so many maps that play good, unique visuals is what is going to separate the gems from the rocks.
You can from just pictures. Think of maps like sculptures. From a picture of a sculpture you can tell how awesome it is going to be in real life. The same thing goes for a map. People don't even want to play it half of the time, they just want to show their friends how awesome it looks, how cool a door switch is, etc. So they download it, share it, and it never really gets played.