The lowest average league bowler to bowl a 300 was Diane Ponza, whose average was 112 when she shot a 300 game during the 1977-1978 season of sanctioned Bowling.
Jim Hosier has bowled 112 perfect games in his career.
70
As of 4-13-2015, the number of 300 games Bob Learn has bowled is 115.
225
It is not a known statistic, however for USBC, you can compare the list of names of who bowled a 300 and how many bowled an 800 and then how many of those who bowled an 800 had a 300.
I don't believe this statistic is kept. The list of 300 games can be found at the Hall of Fame Bowling Museum in Arlington, TX
There is a very long list of bowlers in the IBHOF who have bowled a sanctioned 300 game.
The record for most consecutive strikes in the United States Bowling Congress is 47 and that string included 3 consecutive 300 games. That answer doesn't address possible better strings in the international arena.
Many people have bowled a 300 game. About 26,000 people a year. You can check the USBC website for a listing of sanctioned 300 game bowlers.
tyler selmont.. he has 451 300 games and 213 800 series
Unfortunately there is no way to know this number precisly. USBC has a record of all sanctioned 300's in America, however this do not include 300's bowled for fun or practice or in unsanctioned leagues and tournaments, or before the establishment of USBC. So theres no definite answer.
Bob Learn Jr., has bowled 100 USBC approved 300 games, Last one bowed at 300 Bowl in Waterford Michigan 9-28-2010.