Sad to say, there is no Infiniti model that combines all wheel drive with a manual transmission. If there were, I would immediately trade my 2008 G37S coupe which has only 28k miles. The G37X is so good that I recommend it for those who want, or can at least tolerate, an automatic transmission.
The competition:
BMW 335ix. The consensus, outside this forum, is that they drive better than a G37. Past the end of the warranty, they are extremely expensive to keep running. For example, my wife's nephew had a 330ix. All four window motors and the sun roof motor died under warranty. Long term owners should budget $250 per year for motor replacement. Of course, if you plan to lease, or trade the car by the end of the warranty, this doesn't matter.
Lexus. Another way to spell boring. The only manual is the IS250 which is a real dog.
Audi. After the warranty ends, another unreliable, expensive German car. A manual transmission A4 is slower than a BMW 328 and much slower than a G37. Replacing the twin clutch transmission would require a second mortgage on your house. The TT isn't bad, but I would prefer a Porsche Cayman. The R8 is a true supercar, but I doubt you're in that price range.
Mustang. Pretty good, actually. Read a review of the Boss 302 at
http://www.thetruthaboutcars.com. If I were to buy a Mustang for the long haul, it would have to be a V8. For short term owners, the 300 hp six is astonishingly good.
Camaro. Has independent rear suspension which is better than the Mustang. Personally, I don't like its styling. I'd buy a Mustang rather than a Camaro.
Charger. OK for a big sedan as long as you get a big enough engine. Definitely not a G37. The Challenger is mutch prettier, but still big.
Saab and Volvo. Definitely the also rans. Saabs used to have the virtue of being quirky. The last nice Volvo was the P1800 coupe which was discontinued in the early 1970s. Prior to the advent of hybrids like the Prius, a Volvo was a car for people who wanted to show how much they despise cars.