Game cracks do not usually contain viruses. In 15 years of pirating, Ive caught maybe... 4 viruses? (Oh and BTW, I dont use an antivirus. I use my common sense, verfied sites and communities).
However. alot of antiviruses see cracks as a virus because well... they kind of are. They modify how files work, sometimes change registiries, run under applications so on and so on...