Whilst it is a technological marvel of its time IV was very heavy going and a departure from the sheer zaniness of San Andreas. One thing GTA IV left a lot of people wanting was just some good old fashioned mayhem, carnage and violence. This second game came out around 6 months after the release of GTA IV and that works to it's detriment and to it's benefit.
The first game capitalized on the gaming worlds longing for an open world game during the wait for GTA IV. This was without doubt the peak of the SR series which was likely the most successful GTA clone series ever made. Whilst SR2 was never going to age gracefully it didn't look brilliant when it was new 10 years ago, it's still the same fun romp that it ever was.