Sam Fisher? Isn't Splinter Cell mostly XBOX exclusive... (like one of the very rare titles that XBOX had exclusive, at least)
Anyway, my newcomers would be...
Dart Feld v. Sephiroth [Sephiroth would be trying to kill Dart for his Red Eye Dragoon Spirit, to make himself even stronger.]
Zasalamel (Soulcalibur) v. Raziel (Soul Reaver) [A battle between everlasting entities] Nathan Hale v. Eddie Riggs (Brutal Legend) [Both have been infected with their oppsition's DNA, and use their powers against them]
Raz (Psychonauts) v. Abe [Both have psychic tendencies, Abe could be trying to control Raz at some point, but Raz is able to block him out of his mind.]
Tommy Vercetti (or a GTA 5 protagonist) v. Batman/The Joker/Harley Quinn (Arkhamverse) [See my Tommy v. Joker rivalry on Tommy's movelist.]
Ezio (or Edward) v. Solid Snake [Good ol' Fashioned spy vs. spy logic for this rivalry.] Spyro v. Dovahkiin [Dragon v. Dragon Slayer]
Joel & Ellie v. Nemesis [Nemesis appears, searching for Jill Valentine, when Joel assumes Nemesis to be a severely advanced version of infected he faces in Last of Us]
Pyramid Head v. Ethan Mars (Heavy Rain) [Ethan's constant suffering throughout Heavy Rain, puts him through a temporary fixture within the Silent Hill universe, where he's pursued by PH] --- PSN: MistahRattlehead PSASBR needs a Legend of Dragoon rep. Make it happen, SSM.