A few that I was gonna mention(Custom Robo, F-Zero, Metal Arms, Dynasty Warriors, Kingdom Under Fire) already have been mentioned, So I'll compile a new list straight from my own library.

Zone of The Enders: The 2nd Runner - I cannot express enough how this game is my favourite PS2 game of all time. The action was fantastic, the Cel-Shading was beautiful and the story was simple yet good. I'm a huge lover of Mech Lore within anything, so this game really appealed to me. I consider this underrated because of its poor sales. I just think it had the nasty habit of being made in the wrong generation. Here's hoping for a 3rd installment!

Legacy of Kain Franchise - Rich world filled some dark and grim lore that even now doesn't really get explored that much in current trends(Dark Souls carries that trend, which I really appreciate). Legacy of Kain is by far my favourite franchise that features Vampires, an order of vampire hunters, and dark Lovecraftian-esque Elder Gods. A complex, heavy hitting story that features themes of destiny, fate, Time Travel, corruption and salvation whilst throwing in some of the single most badass vampires you will see in a game? That is why I love it. granted, Soul Reaver 1 and 2 are very outdated, I still enjoy playing through them. fuck Nosgoth though, which ignores all that for a free 2 play class based third person shooter game. Because we haven't got enough shooters -_-.

Kingdoms of Amalur/Dragon's Dogma - These two rough but fantastic gems are super overlooked by a certain few other big name RPGs(Looking at you, Elder Scrolls). KoA has a very flashy and fun combat than most other RPGs do. But I prefer Dragon's Dogma, because that game does big monster battles perfectly. You have to climb up a cyclops, a dragon to really deal some damage to them(Again, unlike Elder Scrolls which you only need a super strong weapon and just slash at the enemies knees). Also, Dragon's Dogma final battle, is one of my all time favourites.

I will add more when I can remember more plus excuse my terrible grammar spelling, it was late when I posted this and I was tired.