There certainly seems to be a few teams who have superior car setups to the rest each year but those dominant teams do seem to change a reasonable amount year on year, at least to the casual, occasional watcher. Vettel didn't win a race in the 2014 season but he steamrollered pretty much everyone the year before right? It seems that the base requirement to be successful over the course of an entire season is to have a good car suited to the driver. I guess there are 5 or 6 drivers each year who could win the championship, if their car is good enough that year. Mercedes seemed to do very well this year, but Red Bull were good the year before and I seem to remember Brawn GP having a monster of a car in 2009 when Button won the championship.
I get what you're saying about 'equipment' having such a big say but drivers probably have more of a personal say in the setup of their car than a footballer does in the design of his boots (although that obviously makes less of a difference for the footballer). In the sense of it being competitive I think it is to an extent, but often individual drivers, regardless of skill level (to an degree), are relying on the other members of their 'team' to make them able to compete with their opponents on the track far more than a footballer relies on Nike or Adidas to make them better footballers on the pitch. Although in a team sport sense, a football team is often no stronger than its weakest player. Is the best 'equipment' given to one team each year in F1 or is it purely down to research and design? I've no real idea to be honest.
As I said though, I'm no more than an occasional watcher of F1, certainly no big fan, and I could well be talking out of my arse on this subject as per!