At least the Spectrum version moved at reasonable speed, the C64 version is really dire and so bad that its unreleased Race Drivin' was to be developed using the action replay camera angle. The colours are very garish too, with yellow on blue to ensure that if the speed doesn't make you nauseous, then the screen display will.
The car also slides around like you are driving on an ice rink, meaning its almost impossible to actually drive on the road. I even think that there was a cheat where you could reverse at the very start and then drive through to complete a lap
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Also "Chase HQ" on the C64. Another port (By the same people who ported Hard Drivin' I think?) of a great Spectrum conversion. The screen size was shrunk, the hi-res car changed to a horrible low res blob, really awful music (Which almost sounds like a censored take because its so poor) and half of the scenery is missing from the Spectrum version.
It's also bloody slow, the turbo boost speed up is the equivalent of the Spectrum version running normally without boost (Well, almost). The presentation is a complete load of crap too, missing the nice bouncy music, speech and bits from the Spectrum game.
At least Turbocharge made up for it...
i nominate the legend of zelda on the NES 
