I've started to find all-pro way too easy. Granted, I've been playing with the PACK recently, but when Aaron Rodgers is getting 12 TD passes and I'm beating the Jags 98-7, something's gotta change. Even if it is the Jags I'm beating. Beat the Texans on the road like 56-10 or something too.
I just play quick passes with slant routes. I audible up at the line and usually make my two WRs run curl flat routes if the coverage is loose. Corners really struggle with the curl flat routes (especially when they're backing off your recievers). If the coverage is tight, I'll just let them run the slants. Usually, a safety steps up (especially if it's a blitz) which gives you plenty of room to throw into. Another thing, I play this type of offense in no-huddle in an attempt to slow the pass rush, but I'm not sure if this makes much of a difference on Madden. Works for me anyway.
I also really like corner strike routes. These things are like cheating on Madden if your offensive line is anywhere near decent. I avoid corner strikes like the plague in the redzone because DBs tend to jump the route and pick you off.
I find that these two methods are all I use these days. They work real well too. I gave up on plays down field a long time ago and find that all other routes are inefficient in comparison (at least in my experience, I'm probably not playing some of them right).
Used these plays to turn my Rams save into a perennial Superbowl team. Then I started a Pack game and the results were obviously even better with Rodgers.
I still struggle with looking after the ball sometimes. I'm getting better in spotting dangerous coverage and not always dumping the ball into it, but sometimes I still have DERP moments and throw really stupid INTs. I'm smashing all records on my Green Bay game (all-pro), but I'm on like 12 INTs for the season so far, whereas guys like Brady, Brees, etc, have around 5/6. That's something I'd really like to improve about my play. It's not all bad, though, Rivers still has more.
: good times. 
Yeah that was the first one I owned too! I played some other ones on NES, but this was the first one I could really get into. 