Example1, that list is kind of meaningless. If you go and breakdown the numbers by age average you get:
28.2 is the average (age of SLG season) of the 62 pre-roids era.
29.8 is the average of the 38 roids age era, and that is including Bonds. If you take out Bonds (He is the ridiculous outlier), the number drops to 28.7.
Now I don't really get the point of the post. We already know that Bonds is a steroid freak. We also know that Mcgwire, Giambi, and Sosa are likely just results of heavy steroid use. Other than those players, there really isn't anything unreasonable about any of the other players in the steroid era. Sure, there may have been players who had a amazing season at a late age, but so have the golden aged players.
You could say Babe Ruth is similar to Bonds in his production in his later years (32,33,34,36,37). Yes, this is a pretty insane and weak statement, but the point is that it isn't unheard of having a great season late in your career.
I also don't get why you highlight guys like Manny Ramirez, Ken Griffy Jr, Pujols, Helton, D Lee, Vlad, and Howard. Really, there is no reason (other than the era they play in) to suggest they took steroids. Manny had all of his best season before he was 30, since then its been downhill. Griffy didn't hit those monster moonshots like the other roiders, he just had a perfect, linedrive swing. The rest of the guys simply had one great season, or have had great seasons while young.
I think it is also important to realize that sports are at the more competitive level than they have ever been. Everyone is strong, faster, and more aware. I would EXPECT players of our age to be superior to players of the older age.
I think there is more to this than just saying "They were on roids, doesn't count". There are the few exceptions (Bonds, Sosa, etc), but I think overall, the consistently great players weren't just the product of steroids. Some may have had the performances increased a bit, but it was only a select few that actually were lifted to ridiculous levels. There is no reason to suggest just because someone has a great season in the roids-era, its just because of steroids, or shouldn't be counted. When it comes down to it, also, the Bonds' of the game were still great players, just not godlike.