I bought these games on Amazon, but i never downloaded or activated the games. Are there any value to these Activation Keys? Can i trade or sell them?

Sword of the Star Complete
Rome Total War Gold
Risen

I know that some games activates on Steam like Dungeon Siege 3, so i can trade or sell those keys, but for the games that wont activate on Steam or Origin, is there a way i can use the keys for trading or selling? Thanks.

I don't think so because the buyer would have to pirate the game data unless you gave them your Amazon account with the games.
Some games have demos that unlock into the full game with the key like Mount&Blade Warband but I don't think any of the games you listed do that.