Let's see if I can type up a list of favorites from memory. These are in no specific order:
Death Valley - Big, wide open, fun TC map. Just all around good. No asset feels entirely useless. Wish games would last longer though.
Thunder Rift (TC) - At first I didn't like this map, thought it was a snipe fest. Have come to love it. Lots of avenues for sniping, lots of side paths for sneaking up and brawling. Can turn quite brutal if one team manages to cap the other team's forward base early on, but I've seen teams come back from that and it makes for an epic struggle. Again, every asset feels like it has a place here, and it's a nice change of pace to have a map with no ASF/VTOLs from time to time as well.
Mirage (TC) - The only complaint about this map is that not all the bases show on the GUI. Other than that, it's a very fun, fast paced map. Far superior to the TSA version, which ends up being just a sniper/missile fest because of lack of incentive to move around the map. Still, even in TSA, this map is playable and enjoyable. BA is fun on this map as well.
Frostbite (TSA) - God I love this map. Lots of cover and multiple routes all across the map. Two bases to spawn from so no real base camping going on. Also, it's just plain sexy looking. (Always loved mechs in snow)
Sandblasted (TSA) - Good for some simple mech action. Hill sniping, missiles, etc. Some people might not like that type of fighting, but it's classic Mechwarrior, really, and there are still plenty of ways you can brawl if you feel the need. BA is also really fun on this map.
Extremity (TSA) - I wondered for so long when I first started playing why people hated this map. Was it the fact BAs have extra mobility? Was it the low grav? Was it the heat during the day? I dunno, I'm still not sure. All of these points make this map FUN for me. Plus, the layout is really interesting, with a lot of ways to sneak up and do some damage, then jumpjet away and live to fight another day. The day/night cycle freezing/thawing the lake and changing the temperature makes you think a lot about where you are and what you're in during what time of day it is.
Also, BA are so much fun to splatter on this map. So many people think that because low-grav let BA fly around almost like ASF it makes them invulnerable... but really, at least to me, it makes them an even easier target.

Those are probably my favorite maps. Next up are my thoughts on maps I find bearable or ok, but I feel could use some work to be perfect:
Kagoshima - Mixed feelings on this map. I love flying ASF on this map, but that's about it. The map feels too cramped and hard to get around as a mech, and tanks seem to rule because of how easily they can hold the two forward spawn bases. Also, not being able to build/repair heavies and assaults at the forward bases is a neat idea, but badly implemented, considering you can still build demolishers and morrigus at these bases. Thus, it becomes tank wars very quickly.
Also, I feel at least some of the roofs of these forward bases should be opened up so that the tanks are a bit more vulnerable to ASF.
Clearcut - I like the visual style of this map a lot. It feels a tad small, and I think it needs a bit more cover in a few places. Trees feel glitchy. ASF have too low of a ceiling and feel pointless with the lack of cover. Nonetheless, have had some good fun on this map, don't hate it, just needs some tweaks to bring it up to the quality of the others.
Marshes (TC) - I think TSA marshes is kinda crap, but the TC one is okay. I'm not sure what exactly annoys me on this map when I play it in TC, but I don't do it very often, people seem to dislike this map. Not sure why. The main landing strip can turn into a bit of a missile fest, but there's plenty of ways around that too.
A decent map that deserves more attention imo. Also want more maps that have capture points that unlock a type of asset like this one. That's a really good idea I think.
Those are my neutral opinion maps. Now on to the two I dislike:
Palisades - Ok, this one at first I hated, because I had only played IS on the map and Clan has such a massive advantage being up on top of the cliff that it was just frustrating. Seemed like a missile fest.
Since then, I've come to enjoy it a little bit more, but all my fun games on this map has been on the Clan side. The IS really need another route to get up to the Clan side of the map with enough cover that they won't get longtommed/arrowed as they're trying to move that way. The IS side is so wide open with so little cover that if the Clan team is all set up it's very hard to push out of your base across that massive open field to make an assault.
I still think this map could use VTOLs or even ASF to help break up the camps that occur.
Inferno - This map is just a hodgepodge of poor design. There are 2 bases for each team to spawn at, but one of them is so far away from the other that it's not worth bothering to spawn there. Everyone knows "the hill" that this map turns into. It's unavoidable. There is absolutely no incentive for players to do anything but alternate climbing the fabled hill and assaulting the enemy lines, only to repeat it a few minutes later.
If one tries to flank around the hill to get behind the enemy lines, you end up coming within range of the other enemy base guns, and take extra damage and possibly have your position revealed, nullifying your attack before it has begun.
I think the spawn bases on this map need to be shuffled around, and some terrain changes need to be made so that flanking lines do not bring players within firing range of the enemy base turrets.
The map also needs to have the bug with the longtom shells disappearing into the aether fixed, so that longtoms can be used to break up hill camps when they occur.
I also personally find the drab brown of this map quite tiresome to look at. I'm sure an artist could pull off the volcanic fiery look without using so many shades of brown. More color would be appreciated.