One of the main draws to AC for me was the awesome soundtrack. Each generation is a little different (old school techno from AC1 all the way to orchestral choirs in AC4) so what are your favorite songs from each generation's soundtracks? And what's your favorite soundtrack of them all?
And better yet, what are some of the great, but underrated soundtracks? Let's exclude 9-Ball's theme and all variations in this too, to keep things fair.
A few of my underrated picks in no particular order:
The ACVD DLC remixes were, in my opinion, amazing. This is definitely my favorite, and made me look back at ACV's soundtrack completely differently (I never liked it much).
It's "That song" from AC1. It took me searching through the entire AC1 OST to find out which one it was, but I haven't gotten it out of my head since first hearing it. The ACVD remix of it is pretty good too. The hyper-aggressive nature of the music stood out against most of the middle energy techno tracks in the AC1 generation.
This was an incredibly simple song from AC2, but it was probably one of the best music-to-mission pairings I ever heard. There's a real sense of depth, urgency, and most important of all, age in it. Up until this point in AC2, you were fighting a rebel who was trying to cause mayhem with the Frighteners. After the final mission starts and you hear this, you realize you're fighting an ancient legend that was destroying ACs before you even existed. It's important because there's sympathy for the villain here, something that is missing in other AC games. It ranks there with Jack-O's death, in my opinion.
This song was only featured on a few of AC3's missions, mostly time attack ones (and a submarine one) but it was hands down my favorite song. Not only was there an incredible sense of urgency, but it fit the concept of "if you don't do this quick enough, you'll drown".
Nexus had a lot of underrated music, the soundtrack was "good" but never quite great. It also had one of the largest soundtracks too. The absolute best on it, I believe, was this song which plays on the final confrontation with Genobee. (can't confirm it, working off memory) but it perfectly embodies the bombastic, overwhelming force that the character was. Most ACs in the previous games were cool because they had a variety of complex weapons, were super-fast and super-sleek and intelligent. Genobee was dumb. Genobee used overpowered weapons, overweight and plus frame, and cheesed grenade launchers, yet was still badass. This song reminds me of that, and makes me want to use dual strekozas and VTFs on a permaglide HW frame in ACVD.
Okay, this isn't technically part of an AC OST, but it was used in the background for one of the Mistcrown flash videos, therefore I have always associated it with AC in my mind. It's just the sort of high-energy ruthlessness that I expect from a good AC game.