With all the differences in playing conditions between ERA's how can we say who the best of all time really is

We can't. It is all debate and conjecture, though many have tried to come up with the "fairest" system of analysis (i.e., using contempory comparisons as a contrived "stat", adjusting for ballpark size and mound height, the "win shares" method, etc.). I once saw a show where a bunch of baseball geeks (like myself) feed a bunch of data into a computer program that then simulated games and matchups (i.e. 1999 Pedro vs 1927 Babe). The point sometimes is not really to reach a conclusion, but to engage in the process of debating the issue.

There is no sensible way to compare pitchers from different eras directly, no. That is why instead one looks at the PEERS of the pitcher in question. Looking, for instance, at Roger Clemens and 3 Finger Brown, there is no WAY to tell who is better at what. But when you look at how each stacks up against his peers, despite the radical ERA of Brown's, Clemens appears to be the better overall pitcher. Even THAT is subjective and needs to be discussed, but times change -- people don't. It is a fools quest to try to find a formula to depend on.

Bill James has some crazy formula and calculates players win shares.(By crazy formula I mean complicated, not insane crazy). He ranked the top 100 players at each position and I think he did a pretty good job with it. He swears by this formula.

His top 5 pitcher all time are:

Walter Johnson - 417W - 279L, 2.17 era

Lefty Grove - 300W - 141L, 3.06 era

Pete Alexander - 373W - 208L, 2.56 era

Cy Young - 511W - 315L, 2.63 era

Warren Spahn - 363W - 245L, 3.09 era

Due to the recent performance enhancing allegations, I dont think it is fair to compare current players to those that played in the past. I think you can only compare for arguments sake and if that's the case, you should take the best from each era and do your comparisons from there.

players now just want strike outs