Depends what you mean by best. The best game has to be F1 2010, in terms of it's technology and gameplay.
But my favourite? Definitely Formula 1 97; a fantastic season in reality, superb car models for the time, wonderful tracks, plenty of tuning options, a progressive damage model, failures, variable weather, excellent AI as well as that legendary commentary from Murray Walker and Martin Brundle.
For me, the only downside to that game is that you can only tune your car prior to a session; so you can tune it before practice, but you have to exit and go to qualifying before you can tune it again. That aside, it is a wonderful game that also has challenging yet forgiving physics. A true masterclass for the Playstation.
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Running a close second is Grand Prix 4. Not a great game by itself, but the mods for it make it a great game. The 1994 one is like the game Grand Prix 2 deserved to be; the 1995 one is alright but it's a b!tch for loading. And oh lord, the 1991 mod is just absolute win.