Mine is purely on National titles, the bowlers listed below have more National titles than the rest. It's also hard to compare as some of the tournament bowled pre-1990 would often attract 120+ bowlers, apart from K&K those days are well gone.
According to the TBA site only 3 Bowlers have won more than 10 National titles (which I find a little difficult to believe), but most of the stats were from an era where there were only a handful of National titles up for grabs each year. Also, alot of tournaments aren't mentioned on the TBA site like the Canberra Open, Cairns, Mackay, Cannington Cup, Hobart Cup, etc.
For the record, I have won 10+ Nationals titles but I don't put myself in the team, nor even close to sitting on the bench with the people listed below.
Male Team
Ian Bradford VIC
Jason Belmonte NSW
Joe Velo NSW
Brenton Davey SA
Terry Wenban NSW
Res: Chris Batson, John Sullivan, Frank Ryan, Brian Bridges
Womens Team
Jeannette Baker VIC
Cara Honeychurch VIC
Carol Gianotti WA
Ann Marie Putney NSW
Ruth Guerster NSW
Re: Amanda Bradley, Maxine Nable, Cheryl Munson