I would imagine Quake would run like crap. Sun is the laughing stock of the computer industry. This is the end of the line with regards to the SPARC series (which was flawed to begin with).
The SPARC is actually a good design, provided you follow the ISA rather than the methods it's been tried over the years. Unlike MIPS or PowerPC, the SPARC's basic design has almost never been followed, instead trying out absurd new concepts in hardware processes and organization without considering the ISA's limitations.
So please, don't bash the SPARC architecture for the failings of Sun. Fuji's SPARC designs, as is the ESA's SPARC design are both fantastic processors, which are robust and solid performers, outdoing Sun's designs easily in most cases.
