So, I don't know what to do with these.

If you ever wanted to give away Darksiders, I would love to play that game!

If you can't find someone willing to trade games you have for games you want, you can trade your links for TF2 keys or refs.
And then use those to buy the game you want from some well-reputed trader.

Those are all awesome games, albeit a little old and bundle material. DS2 is awesome, Titan Quest is one of the best ARPGs ever made, Red Faction is a pretty good campaign FPS, and Supreme Commander... just yeah.

They may not have a lot of trade value, but a lot of people would love those games. You might be able to get a copy of Dead Island for them, but I doubt a FC3.

Try steamtrades and check if someone is willing to trade it

As others have said, those are good games, but they're also bundle material. You can trade them for keys if you can't find a straight trade for a game you want.

If you do decide to put them on SG, you can expect around 1000 entries per week for a public giveaway (for each game).