I'll tell you why. It's the same reason the greatest players in other sports are often compared to the other greats of their era ,who even though they are a rung below are always brought into the conversation. Usually pure jealousy or the fact that said 'best player' is constantly praised. A great example would be Sachin Tendulkar, the cricket batsman.He is deified in India to the point of embarrassment, but he's also that good. He gets compared to lesser players all the time, check out any Guardian thread on him or any Cricinfo piece and most of the comments are "...very good,not as good as so and so" , or "overrated , X has a higher batting average, or Y scored a century at lords".
I too had the same problem with Messi.
This is how I thought of him initially:
I am envious and I hate the fact that this guy the best in the world doesn't play for my club. Why can't he play for my team? Why do I have to worship at his altar? He isn't that good.. just supported by Xavi/Iniesta. Without them he's nothing. But then I saw him play as a teenager, destroy my team for twenty minutes, I loved his speed and power but also the subtle turns and the ridiculous elegance, and then suddenly I thought think 'but wait I hate this prick.'
I started to look for loopholes in his near flawless technique. He can't do anything with his right, can't head (and then he goes and does it against my team in a final ,out jumping your all time favourite 6'6 giant of a player). Two years later he's back ,better , he's done it again. Lucky goal I shout this time and maybe it's true but he's still made two of the best defenders around look pretty average.
Now I accept how good he is.He has this constant relentless need to improve.Every year from the time he was 20 he added something to his game. First it was goals , then acceleration, consistency, freekicks, his vision and range of passing, unselfish play. Now the only thing left is adapting his game into his thirties. But It's not about the goals, it's never been about the goals. Even if he scored 15 instead of 50 a season he would be the best around. His judicious use of his speed and skill, the space and extra 2 seconds he finds on the pitch is what sets him apart. What is so striking about him and Tendulkar is that they can be the best around at two or three positions in their sport. Even if he was a bit of an arse to Ibra and Villa I can forgive him.
I was wrong and I hate to admit it about Messi, he is clearly the best player I've ever seen in Football. I accepted that over the last 2 years, I probably regret that I haven't seen him play as much as I would have liked to, because of midnight Barca games and power fluctuations. I now love watching him play even though some part of me is sickened when he scores a beauty like he did last night or waltz past three players and casually put it in the back of the net like he did when he played Madrid in the semis. I want to shout that the art of defending is dead but I know that's not true. Messi is just that good. I missed the Bosnia game because I had an exam. I got to see him play yesterday and I hope I get to see more of him over the next few weeks. As I get older I want to watch the greatest players of the future generations and enjoy them without the irrational need to knock them or hate them like I did with Messi. I want to go 'HOW DID HE DO THAT?" and gawp instead of saying 'feck it the opposition are rubbish". The same thing with Suarez, I hate the fact Liverpool have him, despite all his antics he's a smashing player and that's why I really want someone like that on my team.
God gave Messi more talent than most and Messi held up his side of the bargain. I can't hate a man who could have coasted and become a bit of a wastrel but became an all time great. To have little talent and maximize it like Gary Neville earns my respect, so does having it all and still persevering.