To be completely honest, I haven't played most of them since I've been busy developing Star Racer. I have seen XF and AeroGPX, and I think they look really great, and I especially think AeroGPX has some legs. Now that I'm done developing Star Racer I think I'll have some time to play it. I'm looking forward to the huge jumps!
FastRMX got me excited when it came out, but I was a bit disappointed by the color switching mechanic, and I lost interest in it after a few days.
The racing game I played the most during development was F-Zero 99, which I absolutely adore. I couldn't put it down for weeks, and a few things in it inspired mechanics in Star Racer. The energy balls that you collect inspired the capsules, and the skyway helped me think through some of the flying mechanics and shortcuts.
My main issue with most of the spiritual successors, and the reason I created Star Racer, was that they mostly seem to try and emulate F-Zero X or GX. I love those games, but the original SNES F-Zero is still the GOAT for me. I still have and play it on my SNES original hardware. I was even analyzing each of the vehicle's handling to see how they made them feel good and was using that as a basis early in development for my vehicle handling.