Being the first to do something well is often enough to make a footprint in history. The original Super Mario Bros. carries a lot of prestige as one of the first platformers many gamers played. It was bundled with the original NES, and later Nintendo Consoles carried on this tradition all the way up to the release of the Wii U with having bundles that include Mario games. The original game was a big success for Nintendo, so they capitalized on it and made him their mascot. What made him stand the test of time however is consistency. While spin-offs to the series are all over the place as is people's reception to them, the main platformer Mario series has delivered consistently tight controls, well designed levels, and delivered solid gameplay. While a few haven't been as critically well received (such as Super Mario Sunshine), they've all been commercial successes. Being Nintendo's flagship product puts Mario into the limelight quite often and thus creates more buzz around it, hence why people talk about it more.
Proof you don't have to be the best at something to be well received or commonly talked about. Not to mention, in platforming, what makes a game "better" is quite subjective.