While its been years since I've played Tecmo Bowl on the Nes, I'm a big fan of Super Bowl and I'm very pleased with how similar this one plays. It features 10 teams (I'm assuming the big ones at the time, like SF, NY and Dallas) and you play through each one in random order as opposed to playing through a regular season. What impresses me the most is how there are 22 men on the field and the gameplay rarely stutters. I've been playing it mainly on my Super Gameboy and I haven't noticed much flickering and it's easy to tell your teammates apart from your opponents. The Blitz games on the GBC should have used this as a template. There is also a two player mode and you do earn passwords after each victory.
If there is a design flaw, it's that, depending on your field position, you can't see down field. If your receivers are off screen and covered, then you run a great risk of throwing an interception. I know in TSB whenever I play as SF I can heave the ball down field and have Rice or Rathman catch it without fail. So if you're running a pass play then you need to read the your offense quickly. Field scaling is an issue all the Tecmo games share, however, and if it's something that has never bothered you before then it shouldn't be much of an issue here.
Not sure if the game I'm describing sounds close to what you're playing on the NES, but if you can find it cheap like I did ($4 loose) then it's an easy pick up.