Which of the Pre-Socratic philosophers had the most compelling ideas?

It was Parmenides and Heraclitus, because they're contribution is that they influenced other philosophers about their notion of the said idea, the first principles of all things. Parmenides believed that everything is permanent, change is only our illusion while Heraclitus argued that everything is in constant change. moreover, this made the other philosophers open.

--- Hareld B. Olita