Well I'm going to need a better reason for inclusion than that. We're not in the habit of including multiple applications of the same type unless they offer different/complementary functionality. And in this particular case fceux has head a better history of continued development.
It's not that easy with emulators - different emulators may have a different accuracy, system requirements, features or support (for example NES has different mappers - some mappers are not supportes on some emulators). So for some systems it makes sense to put more than one emulator into the repo (of course the reasons should be mantioned in the package request ;) ).
In the case of Nestopia: Nestopia has a better accuracy (see here and here). puNES may have the best accuracy (and would also be nice to have in the repo) - but lacks several features that Nestopia has.
Nestopia is the best balance of features and accuracy, and should work for most things. I hope that makes sense. :)
If there can be multiple audio and video players and web browsers that really aren't that fundamentally different from one another, why not more than one NES emulator? Most recent work on the master branch was a month ago, so I'd consider that reasonably active.
@mortemvitae, we have multiple AV players because each of them has their own unique functionality and may excel in certain areas. We still frequently reject requests for AV players when they don't offer anything that the other players do not or do poorly.
Web browsers are a whole different category of special. Google Chrome is currently the most popular non-Microsoft browser on the planet. It provides support for flash and Netflix as well. However, Firefox is also widely used and has a smaller memory footprint that Chrome, which is useful for older devices. Vivaldi and Opera are available through 3rdParty. It's also worth noting that it is important to developers to have access to multiple browsers for testing. We have also rejected several popular browsers because they simply do not do anything better than existing options.
@DataDrake I've to agree with you. There's no reason to pollute the repos with all possible emulators when only a handful of them is actually recommended. If there's any doubt please look at the most comprehensive and up-to-date resource out there - http://emulation.gametechwiki.com/index.php/Nintendo_Entertainment_System_emulators
As you can see, Nestopia is a much better choice than fceux. However, it is already available within RetroArch as pretty much all relevant emulators anyway.
There's barely any setup needed with Nestopia, on the other hand one has to set up Retroarch-which so far I find pretty annoying. If it's the better of the two than perhaps remove FCEUX and include Nestopia UE ?
Well, to each their own. Nonetheless, we have a similar situation with mgba and vba-m. The latter is in fact inferior on all levels but people requested it because it's more popular. It's up to DataDrake to handle it. In the meantime, give RA a try as there's hardly any set up necessary and even gamepads are automatically detected and mapped which is really nice.