He didn't start out very strong as a kid like Vegeta and others. He closed the gap by training with king kai, which was a special opportunity that no one else received except for Yamcha, Tien, etc. and they also improved a ridiculous amount.
From that point on he got by on hard work, determination, and plain luck. After he died during the cell games he had the privilege of training hard in the afterlife for 7 years, which was a much better training environment than anything on earth.
The only instance I see that can be used to prove he had a lot of talent was how far he advanced in the hyperbolic time chamber despite training for less time than Vegeta and Trunks, but it could also be argued that he simply trained smarter than them, giving his body more rest instead of hammering himself into the ground with hard days every day.
What are your thoughts