What game series would you say has the best soundtrack?

Silent Hill (though primarily the industrial stuff in the first Silent Hill), Commander Blood (Jean Michel Jarre in the first game, Stephane Picq in the sequels), Dune (covers both Cryo's and Westwood's games with music by Stephane Picq and Frank Klepacki respectively) and Descent probably.

Quake, System Shock, Cannon Fodder and Unreal are also up there.

I have to go with Halo. Marty O'Donnell is just so damn good.

I'd also put the Elder Scrolls up there.

I'm a big fan of orchestral soundtracks so I personally wouldn't put any chiptune stuff on a personal favorites list but I think Mario and Zelda both have incredible music and Super Metroid has some outstanding tracks. I also am a fan of the Streets of Rage tracks. As far as tracks using more modern styles I would say Hotline Miami was great, but that is only one game. Mass Effect does a great job mixing classical stuff with electronic stuff.

The other series I'd have to mention it Locoroco. Not a series many talk about, probably due to it being a PSP exclusive series but it has awesome music.

Well, Zelda games are always some good listening. But a good portion of that might be nostalgia. More recently, the FEZ soundtrack and the Hotline Miami soundtrack I listen to on a semi-regular basis.

Just in terms of iconic theme songs, Elder Scrolls.

The 90's Rare games also have a special place in my heart.

https://www.youtube.com/watch?v=npuuTBlEb1U

Zelda , Mass Effect , or MGS

The Mario and Zelda series have some fantastic music, but I'm probably going to have to go with Halo. Martin O'Donnell's work on those soundtracks was fantastic.

@fisk0: Re: Descent. Brian Luzietti and those other Interplay guys at their best here, the industrial stuff fit the mood perfectly. The Descent 2 CD audio soundtrack even had a few tracks by Ogre and an instrumental version of Type O Negative's Haunted which is kind of a strange but awesome thing.

And since I could never choose just one, these come to mind...

Unreal 1 (I just love that old-school mod-tracker sound)
Mirror's Edge
Mario Galaxy (can you imagine if Nintendo budgeted all their soundtracks like this one?)
The Last of Us
Fez
Hotline Miami
Sword & Sworcery
Shovel Knight

Oh, and looking forward to Drive Club's soundtrack since I'm a big Hybrid fan.

Indies are just killing it in the music department. I have no idea how this even happens but I love it. Also, game soundtrack remix albums!

The Scythian Steppes: Seven #Sworcery Songs Localized for Japan

Strike the Earth! Shovel Knight Arranged (free (!) but drop them a few bucks anyway)

Command & Conquer

Halo is my favorite for sure.

Your electronic music vector according to Jeff (in the Forza Horizon 2 quick look).

@drzing: Yup, the Descent 2 soundtrack is amazing, but since I always post that in the "what's the best game soundtrack" threads, I felt like giving an example from Descent 1 in this franchise thread. :)

I've had the Descent 2 and Vertigo soundtracks on every MP3 player I've had since the late 90's.

The Download (Nivek Ogre's and Mark Walk's project at the time, not sure why they weren't credited under that name) and Type-O Negative tracks in Descent II were reused from the PS1 version of Descent 1 though. The PS1 version of Ratzes is about twice as long as the Descent II version, and is pretty rad.

Shadow of the Colossus still has some of the greatest music I've ever heard.

Wanted to say Final Fantasy because Theatrhythm. Then I realized, duh, Rock Band.

My top 4 are probably Xenoblade Chronicles (if you haven't heard it stuff is amazing), Persona, Zelda, and FF.