How is goku stronger then vegeta at the end of dbz?

Vegeta has been destroying planets and wiping out races since he was a kid. He was an elite saiyan warrior while goku was a low class fighter who was trained by master roshi and couldn't even beat his brother radditz without the help of piccolo. Plus the fact that even with a kaioken x4 kamehameha and a spirit bomb he couldn't beat vegeta in their first fight. The only reason vegeta lost the fight with the z warriors was because gohan fell on him as a great ape. It's total bullshit. And Vegeta also trained in the little gravity thing like goku but goku still ends up stronger. Vegeta trained just as hard if not harder than goku but since goku fought for love and friendship he got a power bonus.It doesn't make sense