Ohio State currently tops both major men’s college basketball polls. Are they a shoo-in to win the national title? The odds aren’t great. Since seeding began in 1979 four teams ranked #1 in the polls before the tournament won the whole thing, according to Wikipedia:
1982 North Carolina
Since the tournament expanded to 64 team in 1985, the Final Four has never comprised all four #1 seeds, but the top seeds have made it to the Elite Eight 69% of the time. For more stats check here.
If that’s not enough, this statistical guide to office pools
For raw stats, look here.