On PC: Probably Dungeon Siege or Might and Magic: Heroes. Dungeon Siege was the first RPG game I played that sucked me in completely, and it brings back many memories. If they brought an updated version out with better graphics, a new storyline and the same gameplay I'd be first in line to sign up. Might and Magic: Heroes drew me into the Dungeons and Dragons world. I bought and played Heroes 6 last year and loved it. My favourite turn-based strategy game. I don't really play many PC games anymore, however. Every now and again I still fire up my old PS3 and log into DC Universe Online, where I have a Fire Tank that's a lot of fun to play with.
I played a LOT of M&M Heroes... And yeah, I don't get to play a lot these days. Last two times I did, it was Zero-K and the time before Magic Duels.
On the bright side, now my JOB is to write about video games! I'm in gamer heaven! Heh. I have high-hopes for this forum. From experience, I know it's difficult to start an online community, but I've successfully done it in the past. We'll see how LitRPG Forum goes. I mean, we're only on day one or two so far.
Though it's not even in my top 10 list of favorite games, I think I would pick Skyrim. Strictly for its high replayability factor. Especially if you add mods into the equation.
D&D... do i get to pick my DM that is stuck on the island with me? If not, WOW for the communication channel to the outside world. Not gonna try to get off, just figured I could totally troll some folks since I'm on an island and the only way they could find me would mean I got rescued. Sorta.
Most games I've put many hours into are online ones surprisingly If I can have a net connection on the island it would be a tough choice between DAoC and Destiny But for an offline one erm probably something simple like the original Tetris, on the gameboy, as I'd never get tired of it!
Minecraft. I don't know what the deal is but I can play that seemingly endlessly. If there was someone on the island with me, a go board.