The horsepower, 0-60 mph and quarter mile race has been going on, is going on and will be going on. So this side of ultimate will be hard to answer. Top speed record holder is Bugatti Veyron EB16.4 Super Sport World Record Edition(267.857 mph (431.074 km/h)). Fastest 0-60 is Ariel Atom 500(2.3 seconds). Fastest quarter mile is Koenigsegg Agera R(9.3 sec @ 162 mph (261 km/h)). Most horsepower is a rare supercar from Denmark, Zenvo ST1(1250hp).
That's speed and power and whatnot. Reliability, that's hard one for me, I am not really sure which is most reliable. Same with most fun to drive or most comfortable.
Fame wise, you have either Bugatti Veyron or Ferrari 458 Italia.
And looks, well, that's even harder one. Beauty is in the eyes of the beholder, it is said. So there will be many answers to that one. Maybe as many answers as there are people. Some common names that come up often are Jaguar E-type, Lotus Elan, Ferrari 250 GTO, Bugatti Type 57, Lamborghini Countach and Miura, Mercedes-Benz 300 SL Gullwing, Ferrari Dino 206/246 GT, Jaguar XK120 and AC Shelby Cobra.