If you are on windows and have access to this link -
Retro Up Beta then I suggest you use it.
If the above doesn't work and you are on Windows then I suggest these
How to play games at Retro Uprising and
Retro Uprising Game Menu.
Emulators
Always download emulators from the original author. Downloading from a random site is risky.
ROMs
When downloading ROMs always download ZIP, 7Z, ISO or CHD. With a few rare exceptions such as DOS,
ROMs never come in EXEs. If a ROM site is asking you to run an EXE it is a scam, get out.
Links to current (as of 20180830) mostly full ROM sets for most older systems.
For Nintendo use these two links- MEGA Faster. Partially complete set - mostly only recently discovered roms.
- Archive - Slower downloads. Complete set as of 2016. Missing newly discovered games - which are typically rare and less popular games.
The rest are are available via Mega.nz which is one of the easiest sites for bulk downloads.
MAME (Arcade)
No-Intro (Cart/Disk/Tape Games)
Redump (CD games)
TOSEC Computer Games. Huge. Takes a very long time for link to load.