I don't disagree with SCWells either. I'm still trying to include the "luxury" component of the definition. Which is why I chose the Infinity brand over Nissan, Toyota, etc. Sport sedans are a dime a dozen. Qualifying luxury limits the number of options in this category.

 

To me, a luxury car is defined by 3 things: build quality/materials, brand prestige, and equipment.

Build quality/materials:
Most luxury cars tend to have a higher quality of plastics or soft material, fit and finish, premium leather/wood, high quality paint,...etc

Brand Prestige:
Reliability, test of time, recognition over time--the somewhat non-tangible element that a true luxury car should have.

Upscale Standard/Optional Equiment:
Common elements are high quality premium audio systems (with brand prestige--i.e., Bang & Olufsen, Harman/Kardon,..etc), memory seating, power everything (windows, seats, moonroof, steering column..etc), keyless entry/push button start, advanced airbags, voice recognition..etc


To me, Sport is characterized by 3 broad dynamics: Power (Horsepower/Torque/Transmission), Handling (Suspension/Steering/Gears), and Control (Brakes/Wheels/Skid).

I won't go into specifics with sport because it can cross over into subjectivity, but you get the gist.

I think the Infiniti G nails good sweets spots in all six categories between luxury and sport.

 

Aston Martin puts it very well

1. Power: I think it's not just raw power, but the power to perform, which would also include braking, handling and such.

2. Beauty: Inside and outside. Luxurious interior, sporty / elegant exterior.

3. Soul: Prestige of the brand, the class, the recognition.

You just need two more seats / doors

 

M3 or G37, thats end of discussion.