Gameplay wise, all those games were/are failures. (I haven't played MW). You play those games for the story, exploration and quest. Feck, Oblivion and Skyrim's combat is so boring and gay Elton John tried to marry them.
I could never get into MW due to the retardation of the stamina aspect. Yet supposedly the story was amazing as was the exploration (no levelling with char)
Oblivion was an excellent story and I thoroughly enjoyed the playthrough, especially all the side quests and DLC.
Skyrim...not a major fan, boring story, good civil war story, but that for me was it, I just grew bored way too easily.
Witcher brings an excellent storyline, ok side quests, and a rich environment with a relatively decent combat system and magic not being OP as fuck