Only one time in the history of the NCAA tournament have all 4 seeds made the Final Four.
2008.
2 seeds beat 1 seeds all the time.
Total NCAA championship stats below since 1985. Being a #1 or 2 #seed history says you have a 74% chance of winning the NCAA championship. Pretty darn good odds. Getting a #3 seed adds another 13% chance to your odds or an 87% chance.
#1 seed - 19 championships (61%)
#2 seed - 4 championships (13%)
#3 seed - 4 championships (13%)
#4 seed - 1 championship (3%)
#5 seed - 0 championships
#6 seed - 1 championship (3%)
#7 seed - 1 championship (3%)
#8 seed - 1 championship (3%)
Seed's odds of reaching the final 4 since 1985 (124 possible appearances)
#1 - 51 appearances 41%
#2 - 26 appearances 21%
#3 - 13 appearances 10.5 %
#4 - 13 appearances 10.5%
#5 - 6 appearances 5%
#6 - 3 appearances 2%
#7 - 2 appearances 2%
#8 - 5 appearances 4%
#9 - 1 appearance 1%
#10 - 1 appearance 1%
#11 - 3 appearances 2%
What I did find a little interesting is that the basketball world has changed since 2010. Lower seeds have been beating the odds more and making the Final 4.
Since 2010 68% have been a top 4 seed compared with 1985 through 2009 when 87.4% of the Final 4 appearances were made by the top 4 seeds. That'a big decrease. Shows how there is so more parity and maybe guesswork on seeding than the previous 24 years. Since 2010 a #7, a #9, #10 seeds have made the final 4 for the first time ever. SU was the only #10 seed to ever make the Final 4 just last year.