Cyber Empires aka Steel Empire
This game was terribly addictive with hot seat multiplayer ^_^

https://en.wikipedia.org/wiki/Cyber_Empires

I had no idea that Kyd did the soundtrack. That's insane! Now I have to go find out what else he did back then.

Darnit, I thought the protagonist in Azrael's Tear was in a mech but it's just some kind of exoskeleton-y suit thing.

Nope, it's an EA game, according to Wikepedia it started out as a sequel to Nuclear Strike but it turned into it's own game.
I have it and it's a fun game, I like to think I am an ED 209 from Robocop, but the camera is poor which is probably why this game wasn't a great succes.

Then I presume you will love this little biscuit: Remember the epic title music from Blood Money? Now listen to this part from the Amok soundtrack. :D
Oh yeah, read about that not that long ago, totally forgot. For some reason I pictured the box art with a Ubisoft logo.

My best friend had it, we played it a lot in coop and had a total blast. We also played the competitive mode a lot but he always handed my ass to me so that wasn't too much fun... I don't recall the camera being much of a problem, my main issue with the game was the level design. Neither my buddy nor I got past a certain point pretty early on in the story mode. Would gladly finally give it another try. Also we played the German version which had green blood. That was quite silly...

Okay... that's completely insane. And awesome. I can't believe he snuck that easter egg in there.

Mech assault 2?

<span class="bold">Mecha Trigger</span>

It’s a free mech ‘em up where all your movement, aiming, jumpjetting, and laserblasting is controlled by typing commands into a terminal.
It’s hilariously clunky and overwhelming at first, but that’s sort of rewarding.
Have a go!

May or may not be what you're looking for, but some Gundam games were on the Saturn and the Dreamcast. I own a couple, one is the Zeta 2d space ship shooter (you play as a gundam, but it's basically a space ship shooter. Vertical scrolling, like Galaxian I think.). Another is on Dreamcast and it's about what what closest I'd assume to a simulator for a Gundam back then. I like them both, the Saturn one is a little better in that it's more immediate fun but the one on Dreamcast is surprisingly fun after getting past the awkward controls.

Doubt it, while you can steal enemies mech i don't think you could grab enemy parts, besides, i don't think there was any xp system in the game (perhaps multiplayer).

I think he is talking about Front Mission, i don't remember stealing individual parts or returning to base to get a new mech but then again i only played the 3rd one.

Anyway, if the multiplayer was still working i would recommend Chromehounds, it was so good... the memories... i even bought a 2nd copy (full price) when my f%#@ing 360 scratched the disk.

It was Metal Fatigue

It isn't that old but use a really old mechanics from the console classic Virtual-On.

Bootfighter Windom XP SP-2

It is a free game where you pitted with up to 10 mechs at the same time. It can be played offline with bots, or online with players or bots, if you want to fill the empty slots.

Also there are the Ultimate Knight Windom XP, which is an upgraded version of the game with more options, mechs, and better server. Sadly this game isn't free like the prequel. Still my favorite.

Speaking of which, Virtual On is actually a PC game too.

I know, and I really loved it back then. The Ultimate Knight Windom XP however a more advanced game in the same style. You can battle against more opponents. The movements is more corresponding but usually harder to land a hit.

I never played on the PC version, only my friends showed it. As a console game I loved it so much. This is why I like the Windom XP series. It brings back these times and even the multiplayer works perfectly.

I didn't find the information here, but it's certainly worth mentioning that Hi-Rez Studios has released their entire TRIBES franchise as free downloads. The games include:

1994 – Earthsiege
1996 – Earthsiege 2
1998 – Starsiege:Tribes
2001 – Tribes 2
2002 – Tribes Aerial Assault
2004 – Tribes Vengeance

Get them here: http://www.tribesuniverse.com/

I always liked Earthsiege 2 and thought that it didn't get enough recognition. Now anyone can play them - the games are available as DRM-Free ISOs. Enjoy! :)