Before Schnellenburger ( sp? ) showed up The U was about to drop football. The phrase all time makes this list problematic for a program like OU which didnt get rolling until after WW2. Some say the modern era started with the AP poll ( 1936 ). Some say after WW2 (1946 ). I have always thought Nebraska and TOSU were tied at 5th with the others in the top 4 being Ala., ND, SC, and OU...not in any particular order, although the Saban era would seem to me to have catapulted the Tide to #1. Every school has had it's down periods. Its consistency that sets the elite apart.
I agree completely with the bolded.
Any good program can have a championship with a little luck. Few can sustain that and even fewer can sustain that over a long enough period to have a dynastic period and even fewer for long enough to be considered a blue blood or top 10 program.
There are eight or nine programs that are currently relevant and that have a combination of wins, win %, and championships to be considered "blue blood" top programs and all but one are in my top 8. UTe is just on the outside looking in, IMHO and for various reasons the pickings get much slimmer after that.
There is also the problem, as you mention, of different era's in college football. Some, like the IVY League school, dominated the first 80 years or so. Most present day top programs got their start from about 1900-1950, give or take. Michigan had more earlier championships followed by long droughts but still racked up enough wins to by #1 in that category. Even without the titles that take a lot of consistently good football to do that. Even among elite programs there are issues in consistency. Alabama and USC came to prominence at roughly the same time and have followed somewhat similar paths over nearly 100 years, with Alabama pulling away in the last 11 years or so.
If we split things into different era's I suspect everyone's lists would change substantially depending on the era. Very few teams would show up in multiple era's as a top 10 program. Those that would show up more often that not are those four or so top teams of all time. After that long term consistency falls off further and further as we go down the list.
I could break my list into groups of three with Bama, USC, and ND comprising the top tier and each group of three schools being comparable enough that you could place any of those three in any order but each would have a difficult time breaking out of that particular group of three. So Mich, OSU, and OU rankings could go in any order but it would be difficult to place any of those above ND. It would be difficult for UTw, UTe, or Neb to break into that group (4-6). PSU could legitimately be discussed in that group as well.
After that it becomes much more difficult to place teams in the next higher group and 10-20 or so there are a lot of good programs bunched together with lots of strong history and a lot of warts. Differentiating those teams into smaller groups becomes even more difficult and there is little reason to bump a higher ranked program for any of them. These are good programs with occasional greatness.
Enough rambling for now.