I also agree. I've always kind of felt a little jealous of the GT franchise because I've never had a Sony machine, and don't want one, and half the time the races and things are a little TOO serious.
But here's something ... at the end of Sega's 1st Party Life, they made 'Sega GT' for the Dreamcast, and I really wish I still had it because I really feel that it was as good or better than some of the Gran Turismo games, and it had a 'build your own car' mode(with premade pieces of course, but you could also spray-paint the car anyway you wanted, and you could unlock new pieces/engines with different races). And presentation, graphics, and gameplay wise, it was very well made.
After DC died and Sega did a lot of multi-system stuff, they remade Jet Set Radio and Sega GT for X-Box, but I feel like neither held up as well as their Dreamcast originals.
It WOULD be nice if Nintendo would do something...the only problem is, they have no analog-input for gas/breaks, unless they were to actually combine the Wii Wheel with the Balance Board(and you had a chair set at the specific height to let you use the balance board while you sat....or just prop the BB up on something to match your seated height).
One of my ideas for WiiWare(if I could ever do such a thing), was to make a really low-profile racing game that did just that...used the BB and Wii Wheel, but instead of high-class licensed cars, it was all 'Used/Older standard-model Cars', just so that I could put my poor little Geo Prism in the game.

It was just an idea though.
Y'know, F-Zero GX(and even the VC/N64 F0 ) really DOES have some kind of professional-feel to it....but even considering the futuristic setting, it's just OVER too quick. It's designed to be really fast, and it sometimes also becomes its own downfall I guess. Back when the Wii first came out, I had my hopes set for(and bought) that GT Pro Series from Ubisoft, the late-Gamecube-translation with added Wii controls, but it just didn't feel the same. Worse, the cel-shaded graphics looked worse than Sega GT on the Dreamcast, and that's saying something. *sigh* I kind of think Nintendo really isn't up for doing a serious racing game, and I almost can't blame them. But they did do some at least half-way serious things in the past, including Wii Fit, but also things like Ken Griffey Jr. Baseball and the like.