Here is what I posted on my thoughts (with narrower focus) on this last year. It is from this thread:
http://www.net54baseball.com/showthr...=219783&page=2
I will approach this question from a narrowed perspective, because it is within the following guidelines that I have always collected, which is based upon availability of pre-War2 cards. (20th century Pre-1942 cards, for crying out loud).
When I set my self-imposed guidelines, I eliminated all players whose careers were mostly in the 19th century, due to expense. I also eliminated almost all of the executives, broadcasters, etc. due to the lack of availability. Also due to the lack of availability I removed all of the Negro League players. What remains are 20th century HOF players whose careers were mostly before World War 2. The following are the ones I always considered tougher to track down Pre-WW2 cards due to the player being in fewer popular sets during their playing/managing careers.
Big Names:
Honus Wagner - in a decent amount of sets, but less frequently seen because of his absence in almost all the tobacco issues
Eddie Plank - not in that many sets, and incredibly tough in the most popular (T206)
Lou Gehrig - in some more commonly issued earlier 1930's sets, but still not as many as you would think based upon his status
Others:
Willie Keeler: 1910 era cards at the end of his career
Jimmy Collins: in fewer sets than Keeler
Jake Beckley: thankfully in T206 set, otherwise not much available
Elmer Flick: in fewer sets than Keeler
Hugh Duffy: at end of playing career during 1910 era
Joe Kelley: at end of playing career
George Davis: not in many sets
Joe McGinnity: at end of career in 1910
Addie Joss: untimely death in 1911
Jack Chesbro: thankfully in T206 set, otherwise not much available
Gabby Hartnett: in E120, and 1933 Goudey, otherwise surprisingly not in many of the prominent 30's issues (other Goudey, Diamond Star, Play Ball)
Ross Youngs: short career, mostly featured in strip sets
Casey Stengel: not in many of the common sets
Wilbert Robinson: surprisingly in MORE sets than expected
Stan Coveleskie: career falls in the 1917-1932 'dead zone' card era
Bill Southworth: seems to be overlooked in most sets
Charles Comiskey: executive, but featured in prominent sets like Cracker Jack and Sporting News
Branch Rickey: fortunately featured in Cracker Jacks and V100 sets
Bill McKechnie: in limited sets
Ducky Medwick: missing from early 30's sets, and most Goudey issues
Luke Appling: mostly mid to late 30's sets
Billy Herman: besides 33 Goudey, not in many sets
Fred Lindstrom: overlooked in most 30's sets
Al Lopez: not in many sets
Dizzy Dean: short career cut short his card appearances