IV's story would have been completely fine, it had zany missions like kidnapping that crazy girl. The problem is that there wasn't anything TO DO in between missions. Coming from previous GTA's, Saints Row, and Just Cause 2, I just felt really limited.
The previous GTA's seemed to have the serious undertone and yelling and car chases, but then the latter ones were broken up with planes, parachuting, dirt biking to base jumping, etc ... I loved GTA IV, got all the expansions and loved them too ... but the world itself felt too limiting. Going crazy in the city was always the same thing. After SA and JC2 I was used to scenery changes, meta games within the game and such.
I don't understand how people can say GTA IV was 'super serious' ... it wasn't. But I can understand the lack of 'going crazy' because in the end, you were left with a really big unvaried sandbox, but very few toys to play with. I felt myself just going from mission to mission hoping 'something crazy' would open up or I would discover a non-city part of the map to really explore.
GTA V seems to change all that. My favorite thing was jumping on a dirt bike and driving to the top of the mountain, just the long expanses of driving where it seemed like I was travelling 'soo far' within the game.
1 Hour, 31 Minutes.