Erm... Minecraft Technic Pack
Seriously, what about Ys : Origins? It's a great old-school game, you can get it on Steam which is great too.
It's an horror game, and there isn't one the list but it's still a great experience, so let me recommend you Amnesia, on steam. Very atmospheric, and scary too.
In terms of an RTS, I'd say you haven't truly known this genre of game if you haven't played Starcraft I or II, both a great.
Like Pulse, I can't tell you enough to go ahead and get Terraria, it's the second game I have the most hours on, (after Minecraft ), and I had some of the best moments of my gaming career on it's multiplayer.
If you like TES, I think you'd be highly interested by DarkSouls, one of the RPG of the year in my opinion.
That's it for my recommandations's for now, the other would probably be games you couldn't get out of Ebay anyway.
And anyway, is there still anyone on the Age of Mythology servers? Last time I checked, it was deader than Skeletron. It's really a great game, love Atlantis.