It is a very tough decision with that limitation. I would ideally need ~200 titles limitation...Here's the 25 I settled for in alphabetical order:
Berzerk Bump'n'Jump Centipede Donkey Kong Elevator Action Galaga Gauntlet II Ghosts'n Goblins Gorf Indiana Jones and the Temple of Doom Journey Joust Jungle Hunt Moon Patrol Ms. Pac-Man Pac-Land Pac-Man Pandora's Palace Phoenix Popeye Punch-Out!! Q*bert Star Wars Tempest Wizard of Wor
The next 25 would consist of:
Altered Beast Amidar Arkanoid Asteroids Defender Dig Dug Do Run Run Double Dragon Gyruss Mr. Do! Mr. Do's Castle My Hero OutRun Rally-X Renegade Robotron 2084 Route 16 Satan's Hollow Spy Hunter Street Fighter II - Championship Edition Tapper Time Pilot Tutankham Up'n'Down Vs. Super Mario Bros.
I'll stop there - but easily can list another 125-150 titles I would want.