Top 5% = 36% of Both Income and MLB Home Runs
Using the sortable Major League Baseball historical database, there were 1,226 active professional baseball players in the major leagues in 2008, and there were 4,877 total home runs for the season. The top 5% of the MLB players ranked by the number of home runs hit in 2008 (63 players with between 22 and 48 home runs for the season), hit 1,779 home runs, or 36.5% of the total.
Interestingly, in 2006 (most recent year) the IRS reported that the top 5% of American taxpayers earned 36.6% of the total taxable income that year.
In other words, home runs are distributed just about as unequally as income - the top 5% earn a disproportionate share of income, about 36%; and the top 5% of baseball players hit a disproportionate amount of home runs, about 36%.