Somonah said:
I'd go with WipeoutHD. It's cheap, great racing and as for realism, who knows maybe it is super realistic. Maybe that's how racing will be in the future. You don't know. Shut up.
EDIT: Isn't there a cheap version of GT5 that's just the arcade quick race stuff? If there is maybe try that.
I'd recommend Wipeout HD as well. Very fun arcade style racing game, and quite cheap despite being pretty well filled with content. Well worth the purchase.
And I believe the GT game you're thinking of is GT5: Prologue. It's got far fewer cars, I believe coming in around 90 or so if memory serves, and there's less options to customize the cars that are there, but I would honestly recommend it over GT5 myself for the simple reason that the actual driving and race gameplay was flatout better than GT5. GT5 had a disappointing lack of races considering how long it was in development, added a stupid leveling system that made the end game utterly unbearable, and made money a bit too difficult to come by. The AI also didn't get any real improvements from Prologue, and there were so few restrictions on races that it made finding a challenge in the game difficult (which is admittedly a problem with most GT titles).
But Prologue had far more restrictions on what you could enter into races, and the challenge was at a much better level because of it, and because of the lack of customization options. You actually had to get better to beat a lot of the later races, not simply buy/win a better car and power your way to victory like you can do in 90% of GT5.
Overall it was a much more streamlined and rewarding racing experience. If you don't mind not having the huge car roster then get Prologue. If you want the huge car roster, dust off your PS2 (or buy one if you haven't already) and go find GT4, because GT5 is not worth the money unless you want to play online.