The first game I tried is not an emulator but the remake of the 90's game Red Alert, it's called openra.

I downloaded the AppImage, chmoded the file to 755 and it works.

At the first run, it downloads automatically the game data.

Amiga

Then I installed an amiga emulator: fs-uae and fs-uae-launcher I played a few games on fs-uae, it works great.

Atari

The next emulator is an atari emulator, I chose hatari. hatari wants the TOS file to be stored in /usr/share/hatari/tos.img, so I downloaded TOS v1.00 (1986)(Atari Corp)(ST).zip and unzipped it the required directory. I played a few games, it works fine.

Super NES

I installed higan, to run a game, enter: higan ROM.zip

PC emulator

I installed dosbox, to run a game, cd to the game directory and then enter this:

dosbox
mount c .
c:
run game exe

Amstrad CPC 6128

The Amstrad emulator is not in APT, I insalled caprice32 like this:

sudo apt-get install libsdl1.2-dev

mkdir -p ~/Downloads/amstrad/
cd ~/Downloads/amstrad/
git clone https://github.com/ColinPitrat/caprice32.git
cd caprice32/
make APP_PATH="$PWD"

And to run a game (Sabre Wulf in this example):

cd ~/Downloads/amstrad/caprice32
./cap32 ../Sabre\ Wulf\ \(1984\)\(Ultimate\ Play\ The\ Game\)\[t\].zip
cat
run"sabre

Sinclair ZX spectrum 48K

I installed fbzx, not all games I tried worked.

Moon Alert works fine:

fbzx Moon\ Alert\ \(1984\)\(Ocean\ Software\)\[Speech\].z80

MAME Arcade

I installed mame and copied the ROMs to ~/mame/roms/.

To run a game, enter mame in a terminal and choose a game in the list.

To compile the latest version of mame, execute these steps:

git clone https://github.com/mamedev/mame
apt-get install libsdl2-ttf-dev
apt-get install qtbase5-dev

##################
# Add in makefile:
##################
QT_HOME = /usr/lib/x86_64-linux-gnu/qt5/
make

apt command for installing the emulators in this page

apt-get install fs-uae fs-uae-launcher hatari higan dosbox libsdl1.2-dev fbzx mame