http://gamehulu.com/123-games-with-untapped-franchise-potential-classicradar-2/
Ones I agree with
42 Grim Fandango (best adventure game of all time. fact)
52 Outcast (never played but it looks cool!)
56 Dead Head Fred (one of the more interesting psp exclusives)
60 GUN (for so long I have waited for a sequel)
66 Primal (one of the PS2 games I regret not completing. Utterly compelling, unique and just visually so stunning)
67 Forgotten Realms: Demon Stone (never played but looks interesting)
77 Freedom Fighters (always wanted to play this yet never got round to it)
107 Chaos Legion (original wasn't great but had potential and lovely visuals)
112 Indigo Prophecy (heard it was amazing, wish I got the chance to play it)
Would also add Fatal Illusion (Cluedo Chronicles). A very underappreciated mystery/detective/adventure game with an intensely creepy atmosphere. And Orphen, a compelling ps2 rpg that could have been so cool but was too unforgiving and limited. Also Bully, the best action game ever made.