The Sonic tracks aren't live at all? Some of the sounds are pretty realistic.
You mean Project Chaos? It's possible that it was done live, but I've heard some Garritan projects in my composition class and I think that you can get about the same quality of sound as with a live group. Considering that they don't seem to be making any money on the project, hiring a bunch of live performers seems unlikely. (And then getting it all in one take?)
The program is pretty cheap, and it's got
excellent samples. That said, it makes me hungrier for orchestral music like that in my Sonic game, and clearly it can be done without hiring a live orchestra.
If you mean that the stuff in Brawl isn't live, well, yes, some of it is. Sonic Boom has mostly live instruments, and most of the rock-ish tunes are as well. Right There, Ride On is apparently in Brawl and is like a DJ miix (it's from Sonic Rush) and thus *not* live. I don't know if they've done anything except likely improve sound quality.*
Sonic Boom has live instruments as well as some synth stuff, I think, and Super Sonic Racing, like Sonic 3D Blast for Saturn and PC, probably doesn't have any live instruments, just a vocalist and Jacques (Richard Jacques, that is) working with
really good MIDI patches. I can hear these things, and am nearly 100% sure that everything in Sonic 3D and Sonic R by Jacques was done through MIDI (though humanized -- likely he used a keyboard rather than just a tracker or sequencer). The rock tunes are all with live instruments, I believe.
To my knowledge the Genesis tunes minus AIZ are all just rips of sort from the original games and thus pure synth.
EDIT: Yeah, they have at least a bit. AND IT IS JUST SO FUN YOU WOULD NOT BELIEVE IT!