Probably some SNES titles from my childhood that I still play today, like DKC 3, Super Mario World and Yoshi's Island

For games where counting completions is easy, Metal Gear Solid 2 is probably number one, followed by Metal Gear Solid 4. That said, I played MGS4 like seven times the in what was probably a few weeks when it was released and have touched it only a few times after that, so it gets kind of an unfair advantage.

Grim Dawn and Titan Quest are some of the more ambiguous games. I've completed those games probably more times than MGS2 and MGS4... if we count completions on different difficulty levels. However, because replaying the game on a different difficulty level with the same character is a natural progression in those games, I always feel uneasy counting different difficulty levels as different completions.

Other honorable mentions would probably include Half-Life 2 and the first episode of the original Doom as well (curse you, Bethesda, for releasing another game with the same name!).

Likely MegaMan X...

Maybe Chrono trigger or dark souls, I can finish both games in 5-7h, 2h for MMX...

Anyway, I beat all these games +15 times, easy.

Of the top of my head, Final Fantasy 4 and the first Mass Effect come to mind.

Probably Soul Reaver, Shadow Man, Ocarina of Time, Ultimate DOOM, DOOM II, Final DOOM, DOOM 64, Duke Nukem 3D, BLOOD, HeXen, Heretic, Unreal, Castlevania, Contra, Mega Man X4, Metroid Prime, Sonic 3 & Knuckles. Nearly 101st time replayed starting from the 90s.(But except for Shadow Man, which i replayed it 12 times on the different consoles)

Punch-Out!! Hundreds of times beaten

Every 2D Metroid prior to Dread at least 20 times each. I have beaten Dread 5 times since it came out. Wario Land: Super Mario Land 3 must be in the tenths too.

Twilight Princess, Golden Sun 1 and 2 and Kingdom Hearts 1, 2 and CoM at least 10 times each

Pokémon Gold/Crystal, Pokémon Ruby/Emerald and Pokémon HeartGold about 3-5 times each

Xenoblade Chronicles 4 times (one for each version of the game)

Undertale 4 times (PC english, PC spanish, PS4 and Switch)

Bayonetta 2 4 times (2 on Wii U, 2 on Switch)

Final Fantasy VIII 3 times (2 on PS1, 1 on Switch)

Metroid Prime Trilogy 3 times

By far its Resogun, I must have replayed it around 50x already and I still want to get to the top 10 world records. The most addictive game ever created, sometimes I wish I never discovered that game as it takes so much of my time.

But if we are talking mainstream single player games, that will be the very first tomb raider, finished it around 20x, not because it was a great game, but because back then games were shorter and also because I was a kid with no money to buy games so I was stuck on the same game for months until I could afford another.

If we talking games from the past 20 years, I'd say Halo, Alan Wake, The Darkness or Max Payne 3, I've played each at least 5x

I believe my top 4 are
Pokemon yellow (if you also count the 3ds port)
Rune factory 4 (also on 3ds)
And either pokemon mystery dungeon explorers, or magical starsign (both on the DS)

Super Mario World

RPG- Persona 4 including Golden, Vampire the Masquerade Bloodlines. FPS-Bioshock 1 and 2, Half-life 2