Monkey Island.

Everything else is far behind.

X-COM: Apocalypse great strategy game probably the best tactical squad based game ever :) .

UFO: Enemy Unknown great strategy game ground breaking.

Transport Tycoon Deluxe simply Brilliant.

Civ 2 ...the best game ever! ;)

I really couldn't choose a best ever with all of the awesome titles available here, but I will put in a vote for Alone in the Dark. Lovecraftian survival horror ftw. This game used to terrify me when I was a kid...and it is still scary, but for completely unrelated reasons (polygon ugliness).

One Must Fall: 2097>Bioforge>Rest

1. Monkey Island 1 & 2
2. Simon the Sorcerer 1 & 2
3. Doom 1 & 2 (played it every time with a friend of mine on Direct Cable)

Back in 1992 my parents bought me my first PC: flatline desktop 80286 (8 MHz, Cyrus or something), 1024K RAM (yeah, baby!), Hercules graphics card, monochrome monitor, 3.5" disc and a whopping 45 MB HD (which was huge in those days! If people had a HD it usually was about 20 MB). Within a week I had games ofcourse. My first ones were: Sokoban, Bushido: The Way Of The Warrior (which I had to startup using a little tool called SimCGA), Their Finest Hour: Battle Of Britain and Prince Of Persia.

Prince Of Persia looked awesome (even in Hercules!), played easy and was like a movie on your PC: it had it all; action, adventure, cool story. So this has always stayed my favorit game!

Monkey Island? Loom? Lets stick to Loom, as it will probably get far less attention than the other.

UFO:Enemy Unknown is obviously the best one and has no competition in the areas it exists. It combined different genres into one awesome game.

Civilization 1 & 2 i guess. Too bad you can't download them.