Unlike older arcade games, some computer games had an actual ending. Here is a list of games I remember finishing. There are probably more but if I don't remember it must not have been good.
Only arcade game ever finished as well as the computer version - Dragon's Lair. Yeah Dirk!
Ultima 1
The Halley Project
The Secret of Monkey Island
Maniac Mansion
Day of the Tentacle
Loom -- you HAVE to play this..!..
The Journeyman Project
Mad Dog Mcree
Doom 1 full version
Rise of the Triad (shareware)
Doom II with no cheats. (this was an obsession and I still download new wads)