All Mario games
All Zelda games
All Pokemon games
All Metroid games
Almost any entry in the following series: Starfox, Mega Man, Castlevania, Resident Evil, Sonic, Smash, Mario Kart, Final Fantasy, Street Fighter.
But the one game I could always replay is Super Metroid, finished it more than fifty times, I guess, and used to 100% speedrun it glitchless in a bit over 1 hour.
If I like a game I usually play it at least twice. The first run is to get accomodated and to get a feeling of everything what happens, the second run is skill-based and meant to show myself how much I improved over the course of all stages.