GTA IV (for me at least) seemed like the story kinda dived down, then picked up, then diiiived down, and picked up again, over and over. Overall I though it was great, but there were so many dry spots where I had almost completely lost desire to play the game. They do give you plenty of missions to do between people though, which is good. Unless you completely skip one guy, and then have to do ALL of their missions just to proceed. Then it sucks.

Fallout 3 is definitely a great game. Although once I beat it, I kinda lost desire to start again and do all the quests I missed. The level cap is annoying too, but reasonable with the whole use of Perks and skill points. Otherwise within about 20 to 25 extra levels you'd be completely unstoppable, and have nearly every perk at your disposal. You'd think the level cap and inability to switch perks would fuel me to make another character, but it really doesn't for some reason. I tried making an all-melee character but after a while I just ended up maxing out my small guns and using that again anyways.