If you were so inclined to play the actual cartridges again, they have third party systems now that you can buy. I got myself a NES/Genesis hybrid for about $25. The only download is that the controller is basically designed for genesis, which is fine until you try playing a NES game like Mega Man, and the shoot and jump buttons are reversed. :smack:
Abandonware isn’t a recognized legal term, though–somebody still owns the copyright, so downloading the ROM is still piracy, even if the claim is unlikely to be pursued or prosecuted.
I do wonder, though, how long a company can choose not to defend a property before the title becomes public domain (if ever).
If you mean by “only download” is “only downside” (I assume that’s what you meant), another problem for the purists is that those clone consoles never have the original sound hardware, so the pitch, tones etc are quite off for the music and sound effects. This is especially annoying on games like Streets of Rage which are famous for their sound tracks, and don’t sound right.
I sold my Gen Mobile (portable, liscensed Genesis clone) because the sound was mono-only (I have modified my genesis for stereo sound) and the pitch was utterly wrong. 
Why’d you need to modify it? Genesis supports stereo without modification, you just gotta use the headphone jack (model 1) or a stereo A/V cable (model 2) is all.
You mentioned clones having “off” sound. So do most emulators, unfortunately, even official ones used by the companies to sell retro compilations or downloadable games. Nothing beats original hardware in the end, but emulators are just so much easier than digging out old stuff and making sure you have the right AC adapter etc etc etc.
Yes. I’m quite ashamed at that, lol.
On mine - no idea where to find a brand name on it - the sound card approximates it very well. I’m a musician with a fairly good ear for timbre and pitch (no perfect pitch though) and the music is better than on any of my NES emulators. SNES or Genesis, I’m willing to believe sounds more off.
There is no stereo A/V cable for a model 1 genesis, and I don’t have mini-headphone jack support on my stereo receiver, I have to use RCA cables. It is very strange to me to this day that model 1’s do not have stereo sound except for the headphone jack…
I love emulators as well, but Kega Fusion sounds lightyears more accurate than what I was experiencing on the Gen Mobile console. PLUS the D-pad was attrocious garbage, it was nearly impossible to go from left to right without hitting an up or down directional, made playing beat em ups impossible.
Just get one of these 
I could just make one of those with parts I have around if I wanted to, but then my Genesis would look very ugly with a cord always dangling from the front, as-is it has nice left and right RCA jacks on the back (along with my region switch, composite video jack, and PAL/NTSC switch). 
It is not a grey area, ROMs are illegal. Nintendo spends more time trying to bring down ROM sites than other companies. Even if you own the original they are illegal, a lot of sites tell you that you must remove it within 24 hours, again thats a lie. This is no different than piracy. Yes you can make a backup of a CD you own but you are not allowed to download it the two are different.
Has this ever been put to the test in civil court? That is, has anyone ever been found liable for infringement for downloading a copy of something when they would have had a fair use defense for a personal copy they had made themselves? If not, then I suspect that it is a gray area, along with many other aspects of fair use.
Thing is, once you have the downloaded copy, how is it distinguishable from a legal backup? And just because Nintendo goes around trying to stop it doesn’t mean a lot–lots of companies send out those cease-and-desist letters to intimidate, rather than for any true legal purpose. I know of plenty of sites that have gotten the letter, but not taken anything down. And nothing happened to them.
The only way to test the legality is as mentioned above–take it to actual court. You’d think Nintendo would really want to do this, so surely there is a landmark case if they really have a leg to stand on.