Jon probably. Aerys was the king, Rhaegar was the crown prince so Rhaegar's son would come अगला in the line and since Aegon is dead, that puts Jon अगला in line for the throne. But Jon's claim could be weaker if Rhaegar and Lyanna weren't married.
So in short, Jon is the heir to the Iron सिंहासन if Rhaegar and Lyanna were married. If not, then Jon is still a bastard with a weak claim and Daenerys has a stronger claim.