Are there any good comparison tables of all the available chips that support Arduino out there?
Something that compares speed, SRAM, Flash, number of IO pins, package size, etc?
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Vendors like Digikey have a "Parametric search" - you can enter a chip family that you know has "some" Arduino support and find related chips, and then check whether that particular chip has "substantial" Arduino support. It gets complicated, because of all the chips that have essentially "partial, amateur class" support - for example, there's wide and good support for most ATmega and ATtiny AVR chips, but the XMega chips never got much love. And the subset of Atmel ARM chips with support is quite small compared to the number of such chips...
There are in excess of 10000 stocked, current, chips with a CPU core that would theoretically support Arduino with "not too much" effort (AVR, CM0+, CM3, CM4, PIC32, MSP430...)
Also keep in mind that "Arduino"core software isn't really very large or complex. Supporting a significant subset (digitalRead/Write, analogRead/Write, delay, Serial) is pretty easy (and a useful "educational experience" for a new "to-you" chip, too.)
The Microchip website is a reasonable place to start if you want a comparison of the AVR range. If you go to this web page and click on the link for the quick reference guide, you will get an overview of the devices with the details you wanted + many other features of the AVR range.