Personally I’d revive Begone (Nplay.com). It was an FPS game built on Unity engine. I would to play it one more time just to feel the GUI, the servers and the community again. They had cool account systems and forums aswell.
Honourable mentions:
Minibash (a spin-off game to the game Toribash)
Fly like a bird 3 (gamevial.com)
And Attack on titan tribute game(Feng Lee)
Bloody Roar
It was a 3D fighting game in which the fighters transformed into animal hydrids, like a werewolf. It was initially published by Konami and developed by Hudson Soft, but the series stopped in 2003-2004, and a 5th game was planned until cancelled in 2022.
In an era where fighting games like Street Fighter, Tekken, Mortal Kombat, The King of Fighters and Guilty Gear were revived, a returning contender would have been welcomed ^_^
These days, consoles can also manage the transformations easier, in addition of adding more animals to the roster.
God Hand (PS2), a great 3D brawler / beat 'em up, somehow the genre is in decline and haven’t heard of any games tried to repeat God Hand’s style.
Conflict series (PS2), like Conflict: Desert Storm and Conflict: Vietnam, it’s a squad-based third person shooter, you control 4 characters at once, amazing couch co-op experience. Sure we got Ghost Recon nowadays, but the squad control is surprisingly shallow compared to Conflict games, you can’t even manually control them.
Blacklight: Retribution
I had every single cosmetic and easily 3,000 hours in the game. It was my first serious competitive FPS other than Counter Strike: Source
Also, Hawken
Edit: Also, holy shit, Maple Story 2. So underrated that Nexon killed it off.
Too Human. I remember working that demo hard on my 360.
team fortress 2