I think the musous I’ve enjoyed the most and spent a lot of time with are ones that have unique and varied movesets for the characters (the Samurai Warrior lineage of design that tends to be used for the licensed Koei Musous) and have mechanics give me a bit more to chew on than just mashing against mobs.
Fist of the Norths Star structurally works like a regular DW game but I started it on the hardest difficulty available with my Level 1 characters and that turned it into an incredibly tense game. You are so weak and die so easily, and your attack animations are so slow, that I had to plan my actions in a way that you don’t typically expect from a musou. I had learn how to maneuver enemy crowds and myself into the correct positions to get all potential threats into hitsun otherwise I’d risk getting killed mid-combo. Environmental awareness became important because walls and corners restricted the knockback on attacks and let you do longer combos are a larger group of enemies, and they could like-wise do that against me.
Often times, since I was so weak, most moves in my attack chains would not actually cause hitstun, forcing me to position and time my attacks such that I wouldn’t actually reach the enemy until I was doing a mid-chain attack that hit harder and could actually cause hitstun. This was doubly hard against bosses who were the most resistant to hitstun but I found the challenge legitimately satisfying. The enemy variety also kept things fresh, with the variety of projectile enemies and biker enemies and grunts of different sizes. They all required different approaches and strategies when mixed in groups.
The jump cancel system was the most important feature of that game, followed by the Special cancel, and it’s telling that Koei US recognized this and unlocked them by default for every character in the US release. While every character had unique movesets and a unique Special skill, the ability to jump cancel out of any attack is what granted you versatility in combat. You could choose how much you committed to a combo and cancel it with a movement option that worked as a defensive tool, a spacing tool, and a combo tool (jump combos, changing positioning mid-combo, or starting a different attack chain after the jump). Attacks in FotNS had slow animations but the jump cancels made combat feel very fast paced. The second game removed that mechanic and it was all the worse for it.
I put in over 100 hours into that game, constantly losing and retrying levels from the beginning, until I finally beat the main story mode. By that point I had gotten the PSN Platinum Trophy. I never did go back play the Extra Story modes though.
Some other musous I’ve enjoyed off the top of my head: One Piece Musou 1, the Sengoku Basara Series, Kessen 2 (does that count?)