Despite what Americans will tell you, it pales in comparison to Formula 1.
They will try to say that Nascar is better because it has more races, but if they bothered to think first they'd realise that F1 is a World Championship, meaning lots of travel that takes up time. Nascar is confined to America and they don't have to travel far to get to the next race.
Nascar is also very unpopular outside America, someone here said it's getting popular all over the world including Ireland which is a complete lie. It's not shown on any TV channels in Ireland, it gets absolutely NO media coverage and is widely regarded as the laughing stalk of motorsport outside of USA.
They'll also say things like "I'd like to see you drive one at 300kph!". Well F1 cars can go over 370kph on road courses despite over 10 tonnes of total aerodynamic and mechanical downforce, and if you've seen the Monaco GP you'd know how skilled the drivers are to race at over 300kph with metal barriers right next to the track.
If they put F1 cars on an oval they'd be around the 400kph mark. In testing at airstrips they have been over 500kph before, the sorts of speeds top-fuel dragsters do and yet F1 cars have normally aspirated engines, no super or turbochargers, no ABS, no launch control, massive restrictions on aerodynamics and tyres and so on.
F1 is also the richest and most watched sport in the world, the teams spend a combined total of over $2.5 billion per year developing the cars and still make a profit from the sport. It's also watched on TV by an average of 2.5 billion people per race.
They'll also say that races are won at the start and there's no passing, which is total BS. People who say this are just proving how little they know about F1 because there's passing at every race, including the Monaco GP.
So all these idiots who think Nascar is the best are in denial, F1 is ahead in every area.
Rough costs of F1 teams combined (in American dollars):
Wind Tunnel Operation (wind tunnels run 24 hours a day, they never stop developing the aero of the cars): $70,210,000
Car Manufacturing costs: $20,110,000
Research & Development: $175,680,000
Operating cars at tests: $359,680,000
Team Salaries: $313,640,000
Engine budgets: $1,087,500,000
Driver Salaries: $141,100,000
Travel and Accomodation: $82,880,000
Corporate entertaining: $54,150,000
Operating cars at races: $232,060,000
Final cost: $2,537,010,000
Remember, they still make a profit, that's how popular F1 is around the world. Nascar sucks.