How often are top five draft picks actually "franchise" players?
Let's look at some drafts. It's too early to tell with the last two or three drafts, but we can start with 2006 anyway. Here's the draft year, top 5 picks, and the number of "franchise-type" players in the group.
2006 - Bargnani, Aldridge, Morrison, Thomas, Williams - 0
2005 - Bogut, M. Williams, D. Williams, Paul, Felton - 2
2004 - Howard, Okafor, Gordon, Livingston, Harris - 1
2003 - James, Milicic, Anthony, Bosh, Wade - 4
2002 - Ming, Williams, Dunleavy, Gooden, Skita - 1
2001 - Brown, Chandler, Gasol, Curry, Richardson - 1
2000 - Martin, Swift, Miles, Fizer, Miller - 0
1999 - Brand, Francis, Davis, Odom, Bender - 2 (Brand, Davis)
1998 - Olowokandi, Bibby, LaFrentz, Jamison, Carter - 0
1997 - Duncan, Van Horn, Billups, Daniels, Battie - 2
1996 - Iverson, Camby, Abdur-Rahim, Marbury, Allen - 1
1995 - Smith, McDyess, Stackhouse, Wallace, Garnett - 1
1994 - Robinson, Kidd, Hill, Marshall, Howard - 1
1993 - Webber, Bradley, Hardaway, Mashburn, Bradley - 1
1992 - O'Neal, Mourning, Laettner, Jackson, Ellis - 2
1991 - Johnson, Anderson, Owens, Mutombo, Smith - 1 (Mutombo)
1990 - Coleman, Payton, Jackson, Scott, Gill - 1
1989 - Ellison, Ferry, Elliot, Rice, Reid - 0
1988 - Manning, Smith, Smits, Morris, Richmond - 1 (Manning)
1987 - Robinson, Gilliam, Hopson, Williams, Pippen - 2
1986 - Daugherty, Bias, Washburn, Person, Walker - 0
That's 21 years of drafting, 105 picks, 24 franchise players, or 22.8% of top five picks that become franchise players.
I'm sure there will be arguments of the arbitrary designation of "franchise" player. For me it came down to this: "Was this guy, or could this guy be, the best player on a contending team?" If the answer was yes, I gave them the benefit of the doubt.