The league has definitely become more passer friendly since 1980. On the one hand it is easier for a QB to put up big numbers, on the other hand the game has become more dependent on the QB. So that begs the question: Is it easier or more difficult to be a QB today than it was in the 60s & 70s?
Back in the day, a QB who threw a couple of picks each game was not a big problem, now it is unacceptable. I think because defenses and running games were more of the focus back then the QB was less important than he is now (except that most back then called the plays).
Guys like Namath, Bradshaw, Stabler, etc. could throw as many, or more, INTs than TDs and still be winners. These days unless you are throwing twice as many TDs as INTs you are considered reckless with the ball. The top-4 rated QBs in 2009 are all 3-1 or better in TD/INT ratio! Romo is also 3-1 in that stat (24-8).
It is easier for a QB to achieve a 90+ passer rating in today's game but the expectations for a QB are also much higher now than they were in past years. A case in point is the perception that Romo throws a lot of INTs and Aikman didn't. The FACT is that Romo's career INT% is slightly LOWER than Troy's (2.96% - 2.99%). In fact Romo's INT% is the lowest for any long-time starting Cowboys QB! There's a little fact for the haters to choke on.