Tough call but I would have to go with Civilization III. It's a perfect time killer! Plus, you can use it to test out various civilization building strategies before applying them to your real world island...

Hmmm... a Civilization or X-Com?... Civilization or X-com?...

Civilization by the tiniest of hairs.

Tony Hawk 3 on PS2

Fallout 2 -- all the customizable/do what you want fun of the original with an even bigger map, and more guns!!! ;p More death animations too.

Tuan Jim

Battle Tank/City for the famicom

Tribes 2. With all the mods and total conversions out, it is always new. Of course, I would choose it even without the mods. It has all the elements I look for in a game: *playability*, team goals, communication, violence, scoring/bragging, variety of roles, etc. I like the fact that I can play it non-stop for a day, only 30 minutes at a time, or leave it alone for weeks, and still come back to it and be thoroughly entertained by a session. I would rather have a undersea cable connection on the island as opposed to a satellite, I don't like the idea of an additional 500ms of lag.

M.U.L.E. (Commodore 64), hands down.

And I would go with X-Com. I would start to play, look up from the game and 50 years would have passed. Truly excellent. IF it were much longer, I would go with Dune 2.

Custer's Revenge

American McGee's Alice of course

If I was on a deserted island I'd bring Startropics with me. From playing the game, I would learn how to explore caves, attack the monsters with a yo-yo, learn where to find MILK for health and solve puzzles in ancient ruins. Then I'd figure out how to input the password into the sub-c so I can get off the island and get back to my games at home

Mario Sunshine. The games just so damn fun. Plus it's so damn hard that only being able to have and play one game is probably the only way I'd ever get all 120 shines.