To be clear: overrated does not mean bad, okay? though some of my picks for overrated may just be bad in my eyes. Who knows? anyway, my opinion is below on some gems and some duds. 

[b]Underrated[/b]

God-Hand - Made by "Proto-Platinum Games"(Clover Studios, same people who made Okami, got closed down and then people from that studio formed Plat-Games.). It was a goofy as fuck game with a near perfect "martial arts meets Brawl 'em' up" style combat system that rewarded creativity and actually learning enemy patterns so that you can progress the fighting spirit and unlock stronger, badasser moves. It was kinda like the anime, Beat 'em' Up version of Dark Souls before Dark Souls in terms of difficulty. Game got some mixed reviews mainly because nobody wanted to actually learn the combat system, plus as well IGN's god awful review lmao. Worth a check out. 

Street Fighter EX Series - Nothing much to say here really, other than it should've been a completely original series with maybe one or two guest Street Fighter characters. Which it seems Arika is doing with his mystery game. 

Legacy of Kain: Blood Omen - People often go with Soul Reaver 1 and 2, but I think Blood Omen is the best of the series, followed by Defiance. Top Down Action RPG, that still has some of the finest voice acting in a game, even around 20 years later. 

Zone of The Enders 2: The Second Runner - One of my all time favourite games. Fantastic action, fantastic score and a rather simple yet well done story. I still think it was ahead of its time. 

Dragon's Dogma - Does "Epic Big Monster battles" better than most RPGs past or present. You've actually got to scale up the monster and strike him. Love it, wished it got the recognition it deserved. It's a flawed diamond in a rather "Rudimentary" genre of games. 

[b]Overrated[/b]

Overwatch - aka "Team Pixar 2" mainly because it's almost like Team Fortress 2, only with interesting characters that have powers. Prefer Battleborn's roster too. 

Pokemon Red/Blue - It's pure nostalgia with the "Genwunners" Fanbase. even X/Y is better lmao. 

Half-Life 2 - How can an incomplete story be one of the "Best game stories ever" huh? It's really just a glorified tech demo. 

Final Fantasy 7 - mainly because 6 does everything better.