Brilliant? Um, no. Does the ending more or less blow? Sure. But does it have its moments and does it have a serious pair of balls on it? Yep.
Best Defense deserves a (moderately) better reputation than it's been left with. For starters, even though he seems embarrassed to even be IN the movie most of the time, Dudley Moore IS funny in here and has his funny scenes (I miss him). Eddie Murphy (even though his scenes are obviously pasted in) is the 1984 Eddie Murphy that we used to love so much (you can keep the 'Disney' Eddie Murphy of late, thank you) and is worth a few good laughs, and David Rasche (yes... SLEDGE HAMMER!) is a stitch as Jeff (the KGB agent). The scene where David is throwing Dudley all around the bar is worth the price of admission alone (assuming that's a small rental fee for the VHS tape, that is).
It's worth a look, if only because it makes moves that few movies (if any) these days have the guts to make - give it a chance - see it drunk if you have to. :)
P.S. Kate Capshaw is whistling the theme to 'Indiana Jones' in one scene??? Come on, everyone. That's pretty funny.