As a person who likes to review things, I did a quick playthrough of the levels aaaaaaand, well let's take them one by one:
Make a swamp is a very clever and well laid out idea of a huge bassin that the players fight in. Players might try to get to higher ground to see better, but won't be able to see underwater players at all, so it forces the player to think which position is the best one, and the underwater part is well designed in my opinion. Altough I am kinda curious why you chose the night music from Castlevania 2.
HOWEVER, Make a swamp 2 is, unfortunetly, not as fun as the former since it's WAY to dark. I had problem navigating in, but I had a feeling the level is smaller too, altough I like the inclusion of the Castlevania III music.
The Dark Citadel is plain cool in my opinion. It got a kinda Doom 1 feeling with the gothic design and the Petrus Cross with flowing lava (or blood?) The layout is simple, if a bit TOO simple, it's just a square run straight through everything. On the other hand, each section is unique from one another, so that is a big plus. Also like the use of the apocalyptic view outside.
Harvest, is big and full of nifty details, altough I wish there where more furniture or stuff inside the big building. I love the small wheels driving through parts of the level, as well as the feeling of being stuck in a big place. Well done.

Isolated Fear is another cool map in my opinion. I was surpriced when I found the house in the middle of the woods, altough it would have won points if it was darker (not as dark as Swamp 2 thoe) as it would make the player feel alone and hunted. But otherwise, great flow on the map.
Earth Temple... hoboy I DID'NT EXPECT THAT! That place creeped me out, but I love how you kept the dungeon feel and even the puzzles. Especially love the poes and the exit that pulls you up. AWESOME map.

Now... Transylvania. I LOVE DUCKTALES!!! But this map... feels more like a Warehouse than a castle in my opinion. I loved the cart that drives through the alcoves of the place, and the pillair with the Centaur Flash (nice nod to the final part of the NES game. :P) but it's to... square in it's design, alot of the rooms feels to much like big boxes, and some textures are even missaligned I think.
With some massive revamp, it could be one of the best maps ever... hmmm... why not use Castle Dukenstein from Duke Nukem 3d for inspiration? It has the castle feel mixed with teleporters to hidden rooms?
Even if Halloween is soon over, keep working on the map since I believe it can be truly AWESOME if perfected.

And finally... argh... Vesuvius... a level with such an EPIC soundtrack and memorable feeling in the Remastered Ducktales game and... aw dang it's... boring as hell...
Don't take me wrong, it's hard to work with a level whoce only 8bit inspiration is a single soundtrack screenshot, but so much more could be done.
There could be a room resembling the final boss chamber from the original NES game, you could just add a big dingpot to make it resemble the remastered final chamber more.
There could be a tall chamber with a massive pillair in the middle that players can run up through to reach higher ground (perhaps leading to higher floor in the Dracula chamber?) with a great powerup on the middle pillair.
The room with the lava flow could have a balcony area resembling that lava spewing skull seen in the background in Remastered, and could even house some nice bonuses and stuff.
Heck, even some dangerous passages where you have to jump between rocks over lava would have been awesome.
I'm sad to say that as it is, it's VERY dull and uninteresting.
But use the above tips and it could become one of the best if done right.