First thing, others describe their preferences. This gets very personal and you choose your own favorites.
Second: You are going to end up with several Doom engines, so might as well download a few and try them. They are similar enough in their interfaces that what you figure out from one, is applicable to the others.
There are several criteria to select a first choice.
1. Your OS. Get one that was developed on your operating system.
2. Free Look and AutoAim. This is being able to look around and shoot where you look. Vanilla Doom has auto-aim which aims the shots at the monsters. This makes it very difficult to put a rocket where you want it because it will auto-aim at monsters, or not aim at all. With Free Look you just point where the rocket is to go. You can hit a moving monster by shooting in front of it.
3. Jumping. Can jump up on low ledges and jump over gaps.
Vanilla Doom does not allow jumping, so a low wall is an impassable barrier. You have to run across a gap fast enough that you do not fall farther than the step up distance.
4. Network play. Playing with friends requires using the same port (and version). Some ports can play over the Internet, and some only using local networks.
5. Boom compatibility. A set of linedef enhancements that is more widely supported than others. Includes more door types, keys, moving floors and ceilings, crushers, scrolling textures on ceilings and floors, conveyors, etc...
6. MBF compatibility. Having a dog and friends.
7. 3d floors. Vanilla Doom cannot have room over room, which can really hamper level design and results in strange layouts.
In Vanilla wads, Bridges are made using engine tricks, and will not work with multiple players. Enhanced engines have true 3d floors that allow real bridges, and rooms over rooms.
8. ZDoom-isms like sloped floors.
There are several good wads out there, and to play them you will have to download and install the particular engine they need.
For some you may have to install a DOSBOX (DOS emulation).
Doom Wiki has a description for each of the engines, but not all the details, and not always up-to-date.
I have DoomLegacy, PrBoom, Edge, Eternity Engine.
- Boom compatible (the Boom source itself runs on DOS).
- MBF compatible.
- The Boom compatible wads have many more special effects than vanilla wads.
- I am describing DoomLegacy here because the other descriptions you may find cannot keep current with the fixes and enhancements.
- Download the latest 1.44 alpha version from the DoomLegacy site. It is greatly improved over the SourceForge 1.42 version.
- plays Doom, DoomII, TNT, Plutonia, Heretic, FreeDoom, and others
- Video: window or fullscreen, video mode selector,
palette or several RGB modes or opengl
- Has Free Look, Auto-aim as options.
- Has jumping
- Is Boom compatible (almost everything now).
- Has multiplayer network play (32 players). Coop and deathmatch.
- Can play in Teams, with skins.
- Has 3d floors with multiple levels.
- Friction, mud, ice, fog, light effects.
- Quake style control assignments.
- Lots of menus, and a control console.
- Developed on Linux. Default port requires SDL library that you must install first.
- Alternative ports include Windows-SDL, Windows-DirectDraw, Linux-X11, and some others that are in various stages of working (due to no one using them in the last 10 years).
Notable wads that will require DoomLegacy to play.
Twilight - a commando simulation with different weapons.
Phobia - Mystical, Esoteric, a different experience from Doom levels.