2010 - Spain - deserved
2006 - Italy - hmm … not sure, at least definitely not undeserved
2002 - Brazil - deserved, but only due to a weak tournament
1998 - France - deserved
1994 - Brazil - deserved, but uhh, I’m not too sure
1990 - Germany - deserved
1986 - Argentina - deserved
1982 - Italy - deserved, but Brazil and France had maybe the better teams
1978 - Argentina - not deserved
1974 - Germany - deserved, but it’s a shame that The Netherlands did not win a title either
1970 - Brazil - deserved
1966 - England - deserved
1962 - Brazil - deserved
1958 - Brazil - deserved
1954 - Germany - phew, that’s tricky, not undeserved, but Hungary should have made it
The first 4 WCs do not really deserve the name cause too much of the probable best teams did not participate, but still:
1950 - Uruguay - undeserved cause Brzil was the best team (actually the best teams at that time were maybe Argentina and Hungary, which both did not participate)
1938 - Italy - deserved - but it was closer to a EC without the British teams, but now with a good team from Brazil, and without Uruguay and Argentina
1934 - Italy - undeserved - and anyway it also was closer to a EC without the British teams, and the champion of 1930 did not participate, and Argentina played only with an amateur team
1930 - Uruguay - deserved - despite being some kind of America cup with all the best teams from Europe missing, but Uruguay won the Olympic games in 1924 and in 1928, which were much closer to a WC than any of the 1st 4 WCs
Well, all in all not bad. But there were surely some more teams which would have deserved to win one or another tournament.