SINGLE CONTROLLER PORT: You guys will hate me, but I don't think a single controller port was a bad decision.
See, if NEC really thought that multi-player was going to be an important TG-16 feature, you have to create a situation where *a significant percentage of the installed base* literally *buys in* into 5-player concept...
(1) if TG-16 had two ports, it would have been "good enough" and very few folks would have experienced 3-5 player awesomeness of Bomberman (and sequel), Dungeon Explorer (and sequel)...now...maybe NEC/Hudson needed to make a bigger push for at least a *handful* of multiplayer games that were WORTHWHILE...but, honestly, only a few really good games a year would have been fine. NEC JAPAN actually messed up this opportunity because all sorts of wacky multiplayer taps were released (3-player!) when it should have simply been two choices (1) one player for the social pariah and (2) five-player.
REMEMBER...if a developer doesn't see HUGE INSTALLED BASE *WITH* 5-player tap, then developing a game for 2+ people is a dubious proposition (and risky).
TURBOBOOSTER: UNNECESSARY. The NES had composite f*ckING video and and mono RCA OUT. I don't care if lots of Americans didn't have TVs with composite input...BECAUSE NEC WAS SUPPOSED TO BE A FORWARD-THINKING COMPANY and had experience with consumer products in America. Most Americans had a VCR and used composite inputs on VCR for video games, video cameras, etc.
SO, no, I don't forgive NEC for this decision. NES proved you could do it right (TG-16 would be stereo, obviously, not mono like NES).
I had my NES hooked up to VCR, then VCR output to family stereo, by the way. SO, even our ancient RF TV had a relatively "modern" stereo VCR + old stereo (1960's receiver and speakers) = AWESOME experience, despite some old shite. Lots of frugal families did the same thing—we made things work, even if we couldn't afford "cutting edge" equipment "across the board"
(C) Damn, I'm starving. Time for dinner. I have too much in my brain. But this is the CRUX... I really don't think NEC could have been successful without a software library...and if you look at the first two years of games...DAMN, you realize that it was SLIM PICKINS, even for launch in 1989. I feel that the TG-16 would have FLOPPED HARDER if it was released in late-87 or late-88...