I remember the Witcher characters just as well as I do the Skyrim characters, which isn't saying much. There was Triss, who I definitely remember because you see her naked in the first 5 minutes. There was the guy interrogating you. The Kingslayer. Some witch lady? Geralt's two pals who spend the entire game sitting in that bar? Am I at 5 yet?
Skyrim had Lydia, who could forget Lydia? The guy who leads the Stormcloaks who's name I don't remember. The grey beards. I remember some of the Jarls. The Empire commander guy. The dragon on top of the mountain, does he count?
The biggest problem with comparing The Witcher 2 and Skyrim is that the Witcher 2 is a completely linear game. There was probably about 1/100th the amount of NPCs in The Witcher 2. I could probably name every important NPC in Diablo 3, does that mean it has amazing characters that left an impact on me? No, it just means there was a hell of a lot less than other games.