there were so many ports back then... I mainly emulate atari games with either z26win (using the emulaoder interface) or Mess... only thing I really enjoy emulating on my 800xl (or better yet, playing on my real system) is Miner 2049er, Bounty Bob Strikes Back, MULE or Karateka.
and the rest of my favorite atari games were all on the 2600.
Adventure (the first easter egg on a home system I think?)
Raiders of the Lost Ark
all excellent games I've played over and over throughout the years