The thing about comparing eras as unfair is a good argument. The game was different then. I am a middle-aged guy. Whenever I talk to the old dudes (guys my age and older) about topics like this, some of them want to hang onto the good old days and objectivity goes out the window. I have seen a lot of the older retired players talking about how the game is so much faster now and the guys are bigger.
All points here are worth listening to. My point is simple. Football players are bigger, faster, stronger and just plain better than they were just 30 years ago. The young talent today is better. So, if you stand out today you are doing it against better players than we saw years ago.
Back in the day of Butkus the only guy in the entire league who weighed 300 lbs was Ernie Ladd. And he was right at 300. How many 300+ lb guys are out there now? Not just that, these bigger guys are much quicker and faster than, to what seems like, the plodding guys of the 60s.
Again, just my opinion. And it is possible Lewis and Urlacher can get in at the same time. Was Lewis better? I have to say, yes he was. Remember when Lawrence Taylor retired? There were a whole bunch of people who said he was the best LB ever. If that was true then, is it true now? no way.