The Argentina international's words come as a warning to United who, having been defeated by Barcelona in the 2009 Champions League final, already know the threat of the Spanish giants.
Furthermore, Messi's statement comes in a season when Pep Guardiola's side have consistently been dubbed the best ever and the striker alone has scored 52 goals in all competitions.
He said: "This is definitely the best Barcelona team I have ever played in, that's for sure.
"A lot of the players in the team are the same as a couple of years ago, but we are all older and more experienced.
"We have the best coach because Guardiola is just as loyal to Barcelona as the players from the academy. He always does what's best for Barcelona and not for himself. He is a symbol of the way Barcelona wants to play and behave.
"You have to remember that our success is carefully built up through many years. This is the result of years of hard work with the academy players and also getting the right players in the squad.
"It's much deserved that we are winning all these titles and I don't think you will see this team fall down for many years ahead."
The 23-year-old admits he has huge expectations for the final this weekend, regarding the Champions League as the finest competition for any player.
But while confident of an exciting game on Saturday, a glimmer of hope for United's defence is that Messi - who has already drawn comparisons with football icons Pele and Diego Maradona - has incredibly not yet scored in England.
He said: "To me, Champions League is the greatest tournament you can play in, besides the World Cup.
"It has the best players in the world and usually it's the two best teams that reach the final. So it's always a huge privilege to be part of a Champions League final.
"I have big expectations for this match. I have got older and more experienced. I have been in many of the situations before and I take more wise decisions now on the pitch.
"I know what I'm capable of and that means a lot. And I'm playing with a huge self-confidence. I get strange ideas in my head during a match but I'm brave enough to try them because I have this confidence."
Messi added: "I don't know if I'm up there yet with Pele and Maradona. These great players have won so much with their national teams as well and I lack that. Also, it's really hard to compare periods in football.
"I don't have the ambition that I need to hear people say I'm the best in history. If I'm remembered as an important player of this fantastic Barcelona team in 50 years, then I'm very proud."