I'm not a big follower of any sport, but I do find the
Tour de France to be more (personally) compelling than most other sports. I admit I had no interest in the Tour until Lance Armstrong came on the scene -- why bother, it hadn't seen an American winner since Greg LeMond? But I've watched bits of every Tour since Lance began racing, and ever since he's retired from pro racing. Why do I watch? Out of an appreciation for the extended individual effort required (roughly 3 weeks on a bike? 1,800 to 2,500 miles? Over the Alps and the Pyrenees? On the bike for up to 8 hours a day?) as well as the mental fortitude/stamina required to "read" yourself, the Peloton as a whole and your opponents as individuals, and respond accordingly, etc. Some aspects of the race are really "chess played on a bike" while others are basically hours-long "suffer fests" that weed out anyone having a bad day.
Cheating ruins it all... not just for spectators, but also for those riders who are not cheating for whom success in the race seems to increasingly require dishonesty if not outright illegal actions.
As for sponsorships and all, I hear you, but competition in anything requires funding. Even soap box derbies and high school robotics competitions and such have sponsors these days. Many GREAT things can come from corporate sponsorship, evidenced by things like SpaceShip One (Burt Rutan/Scaled Composites space plane... sadly back in the news right now due to an explosion that killed 2 and injured others.) and other contests that advance science or sport. The thing that sponsorship must be accompanied by is accountability because as we are seeing big (corporate) budgets and major pressure to succeed (for one's nation and/or one's corporate sponsor's) equals apparently too strong a temptation for some. Those few need to face severe penalties (stronger than they are right now, indeed), and they also need to be shunned from their respective sports and sponsors to send the message -- to the competitors AND the public -- that infractions are not accepted from any competitor.
Basically, if you want to call yourself a "professional" cyclist/football player/baseball player/NBA player, etc. you need to handle yourself in a professional manner and face legal and financial ramifications when you do not do so, just as one would expect a professional business person to do (not that the average highly paid businessman is a pinnacle of honesty and integrity these days, either...)
There are things that professional sports do provide that are of value to the populace -- a model for teamwork, fair play, personal excellence and integrity, goal-setting and determination to achieve one's personal goals, physical fitness, etc. These are positive things that should not be ignored and should be celebrated; however, when a sport starts to lose its integrity and/or allows the personalities of its participants to overshadow the spirit of the game/sport, it is seriously ill in my book.