Channels like Mugen Guild or SaltyBet are perfect for seeing a character in action before you download them. What Makes a "Top" Character?
A great place for curated releases and finding "Collections" (e.g., "Best of Marvel vs. Capcom").
M.U.G.E.N is famous for characters that look like they stepped right out of a high-budget anime. These chars often use custom sprites and "Full Screen" hyper attacks.