Apologies to the OP but I'm going to have to cheat since we are lumping everyone in F1 together in a single top 5.
Bernie Ecclestone: Very much for the reasons others have stated above. However, I can only place him 5th because for all of the impact driving the sport as a business it is as much due to his monopolising it when it was there for the taking. Like many a business empire it's first served grabs it and the rest is history until someone takes it away, it's sold or the guy dies.
Bernie = No.5
Stirling Moss: I would put this guy as No.2 or 3 if the OP was just about Brit's as his legacy will always be as the bloke who inspired generations of young Brit's to see motor racing as a professional career. Back then this country was so conservative (not the political kind) that the parents of my generation would routinely frown on the idea with the phrase "get yourself a proper job or get out". It's the mark of the man that decades after his enforced retirement, due to the horrifying Goodwood prang, he commands the respect and admiration of any driver worth the salt.
Stirling = No.4
Ken Tyrell, Rory Byrne : Ken was a garagiste team owner/manager/designer whose cars so often went where they shouldn't have been expected to go. Scored championships and gave so many drivers and engineers their first steps on the F1 ladder. His ideas and designs, even those he didn't perfect, inspired and/or were nicked by virtually everybody else in F1. His influence on his contemporaries and the young engineers who came after him cannot be underestimated. Statistically Rory is the third most successful F! designer (after Adrian Newey and Colin Chapman) with more than 70 GP's, 7 constructors titles and 6 WDC's bagged by cars of his design. Would Schumacher have notched up 7 WDC's without him? Who knows.
Ken = No.3.1; Rory = No.3.2
Colin Chapman, Adrian Newey: It's hard to split these two but I'm giving the edge to Colin Chapman because the financial and technical resources available to Newey are light years away from what Colin had to work with. In many ways though they are of the same piece of cloth. Both are reknowned for stretching designs and innovations to the nth degree within banning distance of the regulations, and taking titles hand over fist. Colin also gets an extra nudge due to his being another of the rolled into one team owner/manager/designer and essentially garagiste at heart.
Colin = No.2.1; Adrian = No.2.2
My last selection is as much a surprise to me as he will be to you coming as he does top of my list. Sir Jackie Stewart. Not only is he a 3 times World champion, ex-team owner manager (albeit briefly) but as a driver one of the most influential people on the sport with regards to driving and to safety. Jackie formed along with Sid Watkins and Max Mosley the primal force lay behind the safety revolution that began in the late 1970's and continues to this day. Jackie's part in this revolution was no small beer at the time. He was fighting not only the establishment running F1 but also a good many drivers who had yet to wake up and see the light bulbs. He was also a key figure lurking in shadows of Paul Stewart Racing supporting and advising his son whose team kick-started the careers of many aspiring racing talent. In addition, his business acumen is quite possibly up there with Ecclestone's but he only uses enough of it to do good stuff and have a great life (respect, man).
Sir Jackie Stewart = No.1
Fenderman's Note: Of course all of that could just be a load of old bollocks made up by yours truly after fifty years of F1 mind-altering conditioning ...