My very first run-in with sandbox was Saint's Row 2. That shit was crack. I put down Blazblue and never got back to it because of that game. Its hard to explain really and i never did play any of the Grand Theft Autos but there were so many disturbingly entertaining things to do in that game. Its an interesting feeling when after getting enough police noteriety, that prompts them to roll out the LAVs with machine gun mounts. So then you can steal that shit, take it to the Rim Jobs mechanic and pull out of there with a new paint job, and extra low profile spinners on all six of those giant wheels on that LAV. Hilarious.
I'm playing the new one now and it is good. I'd say its even funnier than the last one with some of the dialogue and radio station comercials but it does take a step back in customization and some missing activities(like street racing). All in all it is still really good though.