When I've used the term it means a shot that I can score on (rare).  It SHOULD mean a shot that is fair but testing, perhaps more testing than fair even.
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"To plunder, to slaughter, to steal, these things they misname empire; and where they make a wilderness, they call it peace."  (Tacitus)

i classify a 'good shot' as a predictable, well-kept, lane-man's creation. your shot will depend on whomever controls the house. i say: good, clean backends on a week-to-week basis, nice lanes (not all dented and pitted from retarded house bowlers), gutters that are forgiving and don't chew up balls that hit the end on spare shots, nice climate control... i dig that.

if the lanes were squeaky clean in the back, with a well-laid shot that wasn't insane (i.e. my house "OOPSING" on the machine, giving us a 50-foot-long LAKE!) i classify it as good. 35-foot wall, 40-foot sport compliant, a PBA shot... i just hate it when they dump oil and don't strip the lanes or maintain the approaches.
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funniest thing i have ever read on here:

originally posted by Bjaardker, about if brunswick sells 2nds/blems:

Yeah, they're called Lane #1s....

JUST KIDDING!!!

And to expand on what deester said, to me a "fair" shot is a shot that:

When you miss your mark by a board to the right, the ball is a board to the right of the desired target at the pins.  When you miss your mark by two boards to the right, your ball is two boards to the right of the desired target at the pins.  A board, left at the mark, a board left at the pins, etc.

Of course, that's a perfect world in which we do not exist, but conditions can be close to this.  Until everyone starts bowling on it, that is.

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Kill the back row (or maybe this should read "make your spares, dummy")