1. City of Mist - It's basically all my favorite things from PbtA, Fate, and Lady Blackbird. The setting is great, but I've been running other settings with it too.
2. The Sprawl - The Cyberpunk game I've been waiting my whole life for, basically.
3. Night's Black Agents (or anything Gumshoe, really) - Spies? Check. Mystery and intrigue? Check, check. Rules light with a narrative focus? Double-check.
4. Iron Kingdoms - The best of the crunchy D&D style combat games. The only drawback is that it's tied so heavily to its setting, which is only a problem if you don't like awesome.
5. Paranoia - If you don't tell friend computer I put this at #5, I'll give you half of m-PZZAT!!

Honorable mentions:

D&D 5e - Honestly, if the GMs I keep getting weren't so awful I probably would have put it at #5. It really is my favorite edition of D&D, even if I don't really like D&D anymore.

RuneQuest/Call of Cthulhu/Dark Heresy/Eclipse Phase - Really any d% based game. They are really decent games, but the rule system, while easy to teach, is really pretty clunky. There's usually a pretty absurd amount of bookkeeping involved too. Basically what a C+ or B- looks like.

Lady Blackbird/Risus - I may not want to play them all the time, but they taught me very important things about how I enjoy playing RPGs.