All three of these models are great cars. Not all three of these particular examples, though. A 318i was always the poor man's (or woman's) BMW, and to saddle that under-powered mill with an automatic is an appropriate alternative sentence of house arrest for a white collar criminal. The 325i in manual would be the correct choice.
Likewise, the Mercedes should not be the no-options-checked version. Every Mercedes owner expects all of the best in tech and luxuries--none of which this particular vehicle has. Sure the Cosworth version would never be turned down, but a proper "regular" 190E makes a great compact cruiser.
The Audi is the closest to best as-is example. Uncheck the sport package. Either buy one without the appearance-only add-ons or upgrade to the 90 (U.S.) or even quattro variants. Audi's interiors bested BMW and Mercedes for years (decades?) and is well exemplified in this era, with a single-piece dash with all the right curves, soft touches and quality materials still not found in cars today--even those with price tags heading north of $40K.
I owned two Audis of the era. First, an '89 100 (the larger size), and later a '94 Cabriolet. The Cabriolet's V6 in the later-year 90 makes for a compelling argument even if it might not be as outright sporty as a BMW with a straight six.