Based on reading:
1. RS4
1a. ISF
1b. M3
I know this is kinda of a cop out, but when you spend this type of money on cars, I think you are really splitting hairs. They are all great cars for many different reasons, all of which depend on the buyer/driver.
I bought an RS4 because I like the buff German car look, with the big flared fenders. Also, there is something to be said for a car that has been significantly changed, engine, body, suspension. Finally, it is in stock now, a few years in production, and can be had for a discount.
Since none of the the other cars are available now, I can only speculate from what I have read:
I think it is a tie between the M3 and the ISF. I love the look of the M3 coupe, but it only looks good with the 19' wheels, the carbon roof, and in lighter colors that show off the contrast in materials. The sedan is kinda funky, especially the back. The interior is straight out of the 3 series, except for the steering wheel. BMW tech is really non-intuitive, and lacks all a lot of the functions of the Japanese cars.
I like the look of the ISF. Yes it is a little crazy looking, in an aggressive way, but again it fits the Japanese style. The price will be a big issue, not just similarly loaded MSRP, but I do not anticipate the "market price" adjustments BMW is known for. Also, the ISF will be a little more exclusive, because I think it will be a "car person's car" whereas the M3, especially in CA tends to be a badge hound kinda vehicle.
Both have a lot great engineering in the engines and suspension, which is really cool.
I like the C63 the least. I am not a fan of the looks. It seems a bit too "Vegas flashy." I also don't like the Top Gear criticisms of the handling. Unlike in Europe, we have a huge history of large displacement, straight line speed cars so I am wary of writers falling in love with a big German engine. Simply put, how much more impressive is the C63 engine in comparison with a muscle car?