Sure, you can make more that 2 hp per cfm if the heads are really good. You can also make a lot less than that if there are other problems.

My 514 dyno mule made over 900 hp with EZ heads that flow in the 360 range so that was about 2.5 hp/cfm. But that was getting close to a max effort combo with 15:1 compression, Q16 gas, dry sump oiling, 0.900 lift cam, etc.

I think the Pro Stock boys get close to 3 hp/cfm with 1500 hp and 500 cfm heads. Most bracket engines are lucky to hit 2 hp/cfm but it can be done if the parts are properly selected.

My 470 dyno mule is making 720 hp with OOTB Trick Flow heads that flow around 330 cfm. That is on pump gas with 10.6 compression. If I was running 13:1 compression and race gas the engine would pick up even more power. So that engine is 2.2 hp/cfm but once again, most bracket guys aren't going to duplicate that engine. It has a belt drive setup and a ported intake and an aggressive solid roller cam. Most bracket guys will dial it down a notch or two to make it more reliable.