[trooper6]

I'm agreeing with L.J. Steele.

1) D&D 5e
2) Fate Core
3) Call of Cthulhu 7th Ed.

These are currently very popular and represent 3 different styles of play.

If you had extra space?
Then I'd recommend:
4) GURPS 4e
5) Microscope
6) Shadowrun 5e or Shadowrun Anarchy