G37...are you kidding me.
I come from the Infiniti world, from multiple g35 coupes and experience with the sedans. My brother has a g37 sedan. I was probably the biggest bmw hater, until I drove one.
In no way is a g37 anywhere comparable to an M3 stock for stock. Now if you want to add all the mods of course it may be faster than a stock m3 but I guarantee it won't feel as stable or as confident as a stock or modded m3.
I feel like Infiniti did a really good job with the 3.7 motor as I really like the way my brothers g37 sedan drives, feels almost a little german lol. However, get it up to some higher speeds and the balance, stability, and confidence just isn't there.
For the price point its a great car hands down and would highly recommend it, alot of bang for the buck. However, if you want to compare against an M3 or even a 335i, I don't see it. I know its not far off stock for stock on a 335i but the reality is, the car just doesn't have the balance of the bmw.
My wife has a 328xi and although its slower than my bros g37 I prefer driving it over the g37 just because of the feel of confidence and stability.