The RSX is front wheel drive and handles like a cow. The other cars I listed because they are rear wheel drive sport cars, not because they are convertibles (the RX-8 isn't). If you can get an Evo for $25k (which is doubtful, since the invoice on a no-option Evo RS is $26k), then you've found a worthy competitor. But I don't think that it's obviously a better car. The Evo wins on power and number of seats, but the Miata wins on handling and convertible top.
As for the argument that the S2000 is more expensive, but it's worth it...yes, I agree! But it's still more expensive, so it's not in the same category. Sure, I personally would go for an S2000 over an MSM, but I'd also never get an Evo RS when the Evo MR is coming soon...more expensive cars, and worth the price difference to some, but not in the same price category that we're talking about.
Defining handling is a tricky business. First you defined handling as the slalom and skidpad numbers. You defended that by claiming that they predict the behavior in everyday situations like lane changes. I disagree with that, too. Those specs simply do not reflect how a car responds to a complex series of inputs or how easy it is to control. In a slalom, you know exactly the path you are going to take, and the inputs are very regular and rhythmic. On the skidpad, you are going around a constant radius, smooth, flat, circle at a constant speed with no acceleration or deceleration.
Then you suggested a subjective definition: how comfortable the driver feels when the car is near its limits. I would propose an alternate subjective definition: how easy the car is to control at its limits. It's a subtle difference, but my emphasis is on "fun" rather than "safety". And being subjective, the results of both definitions will vary from driver to driver. Some will feel more comfortable in a car that will never oversteer, or doesn't lean at all; others like a car that can be steered with the throttle and has a nice progressive controllable oversteer.
Getting back to a more objective way to define handling (since the word is sometimes used to indicate what a car can accomplish and sometimes to indicate how it feels to drive): autocross performance, or as mentioned in your profile, "in da twistiez". It's funny how the non-turbo Miata is the top dog in a faster autocross class than the Mazdaspeed Protege, despite having much poorer acceleration and lower power. There must be something else at work there, and that something else is what I call "handling".