The one I enjoyed most at the time was 1998 because I bought the shirt and watched it with my mates. But I think all things being equal, the top three are:
1970. Peak Brazil, probably a better England team than 1966, Beckenbauer/Muller West Germany, an Italy side based around 60's Inter and the title-winning Calgiari team, plus The Game of the Century, that demolition final, West Germany pulling back a two-goal deficit against England and arguably the best team, goal and save ever. Lots of goals and the small numbers meant it felt suitably epic. There's a great book about the tournament, Back Home, by Jeff Dawson and I recommend it.
1986. The other Mexico tournament and probably the greatest ever conflagration of great international teams. Maradona's Argentina, that formidable West German team that got to six finals in eight tournaments, Platini's French Euro '84 winners, Danish Dynamite, Tele Santana's Brazil (this time with Careca), the World Cup holers Italy, an England team with packed with flair players and, a Portuguese team with six starters for the next European Cup winners some decent outsiders like Spain, USSR, Uruguay and Scotland. Again, lots of goals, some great games and a lot of memorable moments.
1982. Again, all of the above but probably hampered by the stupid rules. Brazil v Italy and West Germany v France up there with the best games ever.
Worst I remember is 2010 but to be honest I don't think many have been very good the last few years. Too many teams, countries that have no business holding it and players who are exhausted.