There are 36 entries in the Super Sentai Series, each of them with the Red leader. In all of those shows, there have been just several suit actors behind Red's mask. Here's my pick for the best ones...
Number One is Kazuo Niibori, of course -- The King of Reds. Mister Red. My favorite suit-actor, period. He's played most Reds in-suit so far, and remains the best. No matter how thin the out-of-suit character is (*ahem*Goggle Red*ahem*), you can always count on Niibori to bring his A game and make that character seem 100 times cooler. Niibori's sword skills not only bring his Reds a samurai-esque presence, but made the sword a Sentai Red's number one weapon of choice. Niibori always brings such a powerful presence and authority to his Reds -- you know Red's the guy in charge, and that he's nobody to be messed with.
Naoki Oofuji -- Oofuji sadly only got one shot at playing Red in-suit, but how memorable it was. In my opinion, he's the closest to Niibori anyone has gotten since Niibori retired, bringing not only the authority, but a smoothness as Ryuu Ranger -- check out those slick fight scenes. What's more impressive is Oofuji's versatility as a performer -- can you believe Ryuu Ranger is the same guy who played Liveman's Guardnoid Gash, Jetman's Black Condor, and then went on to play Carranger's Green Racer? All such different roles, all different kinds of kick-ass. (Yes, even Green Racer.)
Yasuhiro Takeuchi -- Like Oofuji, it's seeming like Takeuchi is only going to get one chance at playing Red, but he made it count. As I said previously, I think Takeuchi's excellent job as Gosei Red in-suit heavily influenced how they started to write Alata, for when Alata was still a nincompoop in the early episodes, Takeuchi never made him anything but a swift, formidable fighter. Like Oofuji, Takeuchi has played a wide variety of roles, and as a long-time fan of his, I knew from roles like Blue Swat's Sig and Gao Yellow that Takeuchi had it in him to play a decent leader. (So, it's sad that people have come to just know him for his quirky and comedic performance as Gokai Green, when Takeuchi has shown himself capable of so much more.)
While I'm glad that the talented Yoshifumi Oshikawa is now in the Red position, he hasn't been given much to do in Go-busters. Still, with his track record (he's done great work as Kamen Riders Gills, Gallen and Ibuki), I think he has potential to become a good Red.
However, everyone else pales in comparison to Niibori, Oofuji and Takeuchi!