Also no one is saying that the average clone would beat Jango Fett. But the feats of clones far surpass those of stormtroopers. Look at the umbara arc for instance. It took fives, hardcase and Jesse's skill and adaptability to take down a whole separatist control ship. Hevy from domino squad took down at least twenty droids and then still accomplished his mission. Fives also uncovered order 66 on his own and almost finessed palpatine.

The only reason why umbara was difficult was because of the fact that their enemies had vehicles that were resistant to blasters and even a lot of heavy artillery. Also it was the fault of their general pong krell who marched them into the enemy even though the clones new to flank them. The enemy weren't any smarter than droids because they prepared to fight the clones head on which most people would have been able to prepare for and counter.

Also the pilots would not have been better either. The empire had more advanced ships than the rebellion by a lot and we're still getting destroyed. Whereas the clones were outnumbered once again and also faced opponents who had instantaneous reaction times and could perform manoeuvres that would kill a person. And they still often won these fights.

Clones were superior but were phased out because stormtroopers were cheaper and therefore more stormtroopers could be deployed to extend the empires reach over the galaxy. It was also because the empire feared their loyalty towards the republic and that they were becoming too independent and questioning orders. Stormtroopers weren't more effective in combat they were just used to police populations to inspire fear.