There is nothing that indicates that the demand for 2D games lessened with the arrival of 3D games. Only the amount of 2D games.
Kirby 64 sold well for a Kirby game.
Mega Man X4, if the VGC numbers are to be trusted, sold alright.
Symphony of the Night became the best-selling game in the franchise, which is something.
Rayman sold really well for a new unproven IP without a massive marketing campaign revolving around it. (Looking at you, Sonic)
And Yoshi's Story sold well too, for a shitty spin-off with narcotic overtones.
And there's pretty much every serious attempt at a 2D platforming, action, adventure or action-adventure game I can think of that sold well. (Didn't include fighters because I don't feel like doing research on the quadrillion fucking Street Fighter spin-offs released 5th gen) Every other game either had a publisher who failed to adequately market or distribute the game for one reason or another, or just... well, sucked. A Super Mario Bros. game published by Nintendo wouldn't have had either problem.
