i think what makes a map good is its difficulty and the number of goals in it. but on the other hand die rise was good for a few weeks then its got boring. my fav motd, i think was so great because there was a ton of things to do, to build, to find, and figuring out what they hid within it,
You can build two things...and one of them (the acid kit) doesn't even need to be built to get an acid gat.
In my opinion, what makes a map good;
1. Plenty of objectives with fitting rewards. MotD did a good job of offering lesser objectives with some nice rewards (Redeemer/Spork), while Sangri-La and Moon offered a larger reward for a larger objective (1-4 players with permanent perks). I'd like to see a combination of the two; one large easter egg with a big reward, and a plethora of side objectives with smaller rewards.
2. Speaking of objectives, an idea I thought up off the top of my head was "High Round Content" or "Round-Specific Unlocks." For example, after hitting round 40 or 50, perhaps another part of the main objective, or another side objective, becomes available. And after 55, another opens up. Perhaps a special area opens up after round 60/70/80. Once you've done everything available to you on MotD, you realize it's only round 20ish and all you have to look forward to is 80-120ish rounds (best case) of zombie-slaying. I think it would be cool to have something to look forward to doing when you hit the higher rounds.
3. Interesting location/setting. Does it have to be as crazy as the Moon or Buried? No. It can be very simple, like a sprawling farm (instead of boring Survival Farm), or it can be crazy like Atlantis!
4. Some kind of boss. Personally, I liked George (CotD). You could kill him, and he'd drop power-ups/perks. Frickin' awesome. I'd like to see more of that.
5. Helllhounds, or a "Max Ammo"/"Perk Bottle"-dropping counterpart. Hounds are classic. Can't go wrong with them, in my opinion. Monkeys and Jumpers were annoying, but that annoyingness paid off in the form of a perk bottle if you could kill them without them touching a perk machine (monkeys) or by knifing them (jumpers). In any case, I'd like some kind of interesting break from the non-stop waves of zombies every now and again. Plus, it's a nice way to keep ammo stocked.
6. Good map layout. I'm not a tight corridors kind of guy, though I don't mind them in small doses. I'd rather have open areas to run around, and not just because it'd easy to run zombies. The last 2 maps have been clausterphobic, and Buried looks to be following suit (Die Rise-tight corridors and elevator shafts, MotD-a prison, Buried-underground ghost town, probably tight areas). I miss areas like the Biodome (Moon). How about a sprawling field in a farm? Or maybe an open area, like Tranzit, but without Denizens?
7. Funny characters that contribute to the story. Nikolai was awesome. Let's bring him back! How does he fit into the story now? Uh... guess what! You're in an endless loop, but it's not in Hell... it's in Nikolai's mind! It was all a drunken, vodka-induced dream! You see, Nikolai finished the bottle of vodka you gave him and passed out while being teleported and he dreamt of exotic jungles, area 51, the moon, a town, a farm, a bus stop, a power plant, a high rise building in Japan, a bunch of guys in the 1930s trapped in an endless comic book loop in hell disguised as Alcatraz Prison, and even an underground western ghost town! "Ugh.... I'll never drink that much vodka again......... DOES ANYONE HAVE ANY VODKA!?!?" And with that, you head on over to Atlantis with the old crew. "I hope the Vodka isn't watered down here.... get it?!"
7 is for laughs.