Yondaime12

Wow! I love it. Great that they reached out and that you're doing the give away. I got Fallout 3 and NV as soon as I saw the sale. The Steam version was very lacking. Glad to see them up there on GOG. :)

100% I'd have to say Morrowind. Even now I go back to it, even if it's just messing with mods and changing them to my liking. :D There are some really good ones out there. Planescape: Torment, Neverwinter Nights, Baldurs Gate I loved story wise (but gameplay is just not that great). Final Fantasy has really great gameplay imo, but story is mostly iffy. Fallout 1/2 or Bastion would also be strong contenders... tl;dr, I love RPGs, hard to choose. :D

Getting DA2 would get you the most content for your bucks, but arguably it's worse content that'll last longer than getting DLC for the other games, since from what I remember they were really good. What I'd tell you is instead to get other games from BioWare. Like Neverwinter Nights! Maybe Baldurs Gate, if you haven't played those games. :) (you can get them on gog or steam. They even have enhanced editions that overhauled the older games)

People seem to have forgotten about the good old Ultima series? Try Ultima 7 (from gog for example) if you haven't already! Witcher 3 kinda falls into the criteria, just not on 3. (although you can sort of choose how your Geralt acts, you have to play as Geralt of Rivia.) The Souls series also sort of applies, but it's more difficulty gated rather than completly open-world. There is also the game "Inquisitor" It's in the style of Baldurs Gate or the newer Pillars of Eternity...but it's not really all that good. If you really enjoyed these type of games I say go for it as well.

Morrowind! By far my most played game of all time, but I really loved Pokemon Red/Blue. Planescape Torment, Diablo 2 and so many great game I can remember playing as well... good times, good times.