My preference would be:
G37 > 328i > C300 > A4 2.0T

Since you mentioned price and reliability and everything else under etc. I think G37 scores highest in price/reliability. Here are the prices according to Carsdirect.com of a relatively fully loaded cars:
G37 – $35,784
328i – $42,665
C300 – $43,798
A4 – $38,570

So, comparably equipped, the G37 is ~$3k-8k cheaper than the Germans. Even with the free maintenance of BMW, you still won’t make up the $7k price difference, especially if you stick to their maintenance schedule.

If you plan to keep the car well past 100k miles, although I don’t have personal experience w/ the BMW or Audi, I can say Infiniti is much more reliable than the Benz and much cheaper to maintain after you’re out of warranty too. FYI, if you buy the Infiniti, you can always bring it in to any Nissan dealer and they’ll maintain it for you, since it shares a lot of parts w/ the 370Z. It’ll save you a lot of $ in maintenance if you don’t care about being pampered. Mercedes tried to charge me for a $900 oil change once.