I saw how much Euro 2004 dramatically upgraded Portugals football stadiums and infastructure? Does the tournament usually do this in every country it is played in?
Depends if the country has enough big clubs already and if the stadiums have been modernised. Where is 2008, btw?
If the government cash out the money, yes. There was no secret "Euro 2004" organization that magically upgraded the stadiums. Uefa sets minimum requirements that have to be reached and the host country governing body acts accordingly.
2008 is in Austria and Switzerland. At least in Zürich the stadium is almost completely rebuild and I think a few other of the 8 stadiums are also rebuild or completely new.