The 56-year-old - who has had to put up with critical headlines ahead of the kick-off on June 8 over fears of racism and claims of poor ticket sales in both host countries Poland and Ukraine - explained the Spanish and the Germans had that bit extra than their 14 other rivals.
"In terms of favourites, I always make the difference between those who can win and those who are difficult to beat," the former French football great told AFP.
"I would put Germany and Spain in the first category and in the second one practically all the other teams, because playing against Denmark, Portugal, Italy and France will be tough, one shouldn't forget that Greece won in 2004."
Platini, who coached France at the 1992 Euros where they failed to impress, highlighted where he felt the Germans and the Spanish had the aces over their rivals.
"Spain has huge experience, Germany is a little younger, and is hungry for success," said Platini. "Spain would like to retain their title with an outstanding generation of players.
"We will see extraordinary matches with teams who came through qualifying without dropping a point, and with players that are extremely strong.
"But is not for nothing that they (Spain) have already won it."
"At the last World Cup Germany made a good impression, but came across a good Spanish side in the World Cup semi-finals to whom they lost.
"It is evident that these two sides have something extra."
Platini, who said the Dutch were just behind those two but needed to step up from being perennial contenders, said he felt that England would suffer more from the absence from striker Wayne Rooney in their first two games - he is suspended - than the sudden departure of coach Fabio Capello in February.
Capello, who had guided England to the finals after a disappointing performance at the World Cup finals, has since been replaced by the well-travelled Roy Hodgson.
"I think that the absence of Rooney for the first two games is much more of a handicap than the departure of Capello. Rooney is one of the best players in the world."
Platini, who has been in his present post since 2007, said that obviously it would be better for the host countries to stay in the competition as long as possible in order to keep local interest burning.
"We have to be neutral, us the organisers. When the local team is in the competition for a long time, there is a better atmosphere, more passion, that is true, it is a fact.
"But it is a competition, may the best team win."