Yeah, Infernape, Magmortar and Heatran were the only Fire types introduced in Gen IV. It makes sense for Fire to be a scarce type, but seriously, only 3 new ones (one of which is a legendary, an awful looking one at that)? That's far too little.
I still stand by my opinion that Game Freak dropped the ball a bit with the Gen IV Pokemon. They redeemed themselves with Gen V. Just my take on it though.