Only 1 game per series - I try to make this list relatively small, ca. 25 entries, so multiple series entries would make things difficult.
Not ranked, because I find that tough to do regarding the different genres.
Edit: Sorted in alphabetical order (ignoring a/an/the) because I like some kind of order.
-- currently working on a bigger and ranked list that won't see the light of day for a long time, but these games here will be part of that, too --