Contrary to common belief I reckon I can give a very balanced view on this one because I actually quite like football! However, I may just be a little biased to horses.....
The main problem with this one is that football's a bit cheaper than horses. 4 jumpers for goal posts and a ball vs well, ermmmm... a lorry, tack, horse, feed, field, stable, entry fees etc etc etc. I think horses lose on that front - only slightly though!
Let's look at the people who play the different sports. It's often said that horse sport is a lifestyle rather than a sport. You can apply that view to most sports though. I would tend to say getting up at 5 every morning to swim before work means swimmers have the lifestyle of a reptile rather than a human. Horses may take up lots of time but by the time you start playing other sports full on they end up being time eaters as well. Officially statistics show that the diversity of people within horse sport is vast. I'm not talking about the demographics of grand prix dressage which are of course fairly skewed to the upper end of things but horses as a whole. Football equally has a vast array of followers across the globe and throughout history. The friends you make in both sports stick as well. In football it's easier to see how friendships form in a team game but look at those in eventing and you see a different kind of strength behind friends. Look at the high levels of equestrian sport and it becomes more apparent that despite internationals being the most competitive places on earth competitors are far better off together, not just because it helps psychologically but because we're better together. We learn so much more by discussing things rather than tackling them on their own.
Then there's the similarities that you just can't deny. At high levels both sports see money change hands in vast volumes. Whether it's the latest transfer fee or the most recent *** horse sold. The cultures also similar in places, everyone knows how to have fun. Perhaps footballers seem to get into the press more because of it though! That drinking culture that we're all banned from talking about is there in both sports as well. Plus, there's the glory. Score a goal in the champions league final or win Badminton, either way you end up heralded as a God in one form or another.
However, horse sport has that something special. The "je ne sais quoi" that only the photo of someone dropping into the lake at Badminton or mid air over the puissance wall displays. The thing is with horse sport is that you'll never be alone or else you'll be walking. The most successful combinations are very often the best teams, the ones that click. Watch the best horses with the best riders and you'll see what football lacks, the connection between horse and rider that is totally unreproducible anywhere else. Let's face it. Horses weren't born to do piaffes, jump steeplechases or jump ditches. I reckon we're on to something special here.