So what is a respectable OPS or WAR? Which numbers should impress me here?
Houston-Nat broke down WAR well enough. As for OPS a better stat to use is .wOBA (weighted on base overage). It's more complicated to calculate but the general consensus is that it is more accurate as OPS weighs slugging and on base percentage equally when it has been shown that being able to get on base is nearly twice as valuable. wOBA accounts for this. Plus it is on a scale we are more used to (OBP).
But to answer your question anyway, it really depends on position. An OPS or wOBA that's considered great at one position (SS, CF) may be mediocre or worse at another position (1B, LF, RF). Here's a quick scale for reference:
OPS:
Excellent - 1.000
Great - 0.900
Above Average - 0.800
Average - 0.730
Below Average - 0.700
Poor - 0.600
Awful - 0.550
wOBA:
Excellent - 0.400
Great - 0.370
Above Average - 0.340
Average - 0.320
Below Average - 0.310
Poor - 0.300
Awful - 0.290
SOURCE:
http://www.fangraphs.com/library/index.php/offense/