Ok, many of these answers are not Renaissance artists! I have an art history degree and I'd say your best bets for best artists are (as others have said) Giotto for early Italian Renaissance, Leonardo and Raphael for High Renaissance, but also check ...
Try Wikipedia -- their list is pretty extensive, and includes a fair number of widely successful thinkers from before the European Renaissance -- sort of pre-Renaissance Renaissance Men.
Thank goodness for renaissance artists - they broke the mold and taught other artists (as well as viewers) how to SEE. I know a few artists who paint in this traditional style (heavy lighting, muted tones) and sell very well. It's all in the techniqu...