I've given my opinion on Simpson in a couple other threads, but I'll throw it out there again as a Bengals fan.
I think he ends up with about 50 catches for 750 yards and 6 TDs. He'll put up a healthy YPC and score some TDs, but I doubt he has a big reception total. He's a much more attractive sleeper in standard scoring leagues in my opinion because he's a real threat in the red zone.
Shipley will get more catches (65 or so) but have less yards and fewer TDs. No value in standard, but definitely has some sleeper potential in PPR.
AJ Green will step in as the #1 WR immediately and have a much better season than many seem to think. I'll predict 75 catches, 950 yards, 9 TDs.
Gresham should put up solid numbers, but I suspect they'll fall just short of the top 12. Maybe TE15 or so with 55-650-5.
I understand people trying to avoid the Bengals in fantasy, but I think its a mistake. The schedule is much easier than last year. The defense will likely be pretty mediocre, but that just means they'll be behind a lot and could put up some garbage time numbers trying to come back. I also think there's a lot more talent at WR/TE than people realize.