Note: All of this engines require the original game data files as they are work based on reverse engineering of the game binaries but all content must be installed by you. You can find most games quite cheap at either Steam or Good Old Games.
I love videogames, but lately I'm noticing that out of the dozens of monthly releases, as much as one title per month is appealing to me. While this is good for my lack of time, it also means that with some exceptions, I'd sometimes rather play an old videogame instead of the latest triple-A. But, as Windows evolves compatibility breaks, and regarding old videogames many times the only available trick is to fallback to DosBox. You setup everything, launch it... and notice that playing Dungeon Keeper at 320x240 was acceptable back then but now feels way too low for a strategy game.
Ohh, nostalgia, always tricking our mind into feeling that old games were superb and awesome, but also forgetting that UIs were more ankward, resolution was pretty low, and games had also bugs (although not so many as today constantly-patching madness) and severe limitations. Thankfully, there is an answer for this wish of "playing old videogames fixing old times annoyances": Fan-made game engine recreations. Crazy developers that rebuild the game internals either as a multiplatform game (Windows/Linux/Mac) or at least compatible with the latest Windows versions (still a great achievement considering that many were made for MS-DOS), but usually also offering higher resolutions, working online multiplayer, tons of bugfixes and usually also some tweaks or improvements over the original.
Here is a small alphabetical list of 12 classic games that I love playing with custom engines because they recreate quite well the experience or when they enhance it, it really is for good.
- Diablo 1 HD Mod: Diablo had lots of unfinished quests and even some art. The Green Portal (unofficial) and Hellfire (official) expansions added content, but this mod not only joins those but also fixes all known bugs and half-baked quests. It also has a crafting system, adaptative difficulty level, 3D acceleration and visual effects like colored lights, so it "transforms" the original but takes it almost at the level of Diablo 2
- Dune Legacy: Dune 2 was the game that made me "want to do similar things with computers", to decide to study computer science. Dune Legacy allows not only the full campaign with higher resolution and better UI controls, but also multiplayer and skirmish games
- FreeCiv: Civilization was one of the first PC games I enjoyed on my 386, so many afternoons spent deciding tactics to conquer the world. This version not only has multiplayer but also supports modding via custom rulesets. Deviates a bit from the original as contains elements from Civ 2
- FreeSynd: This is the only game of the list that I wasn't unsure to add, because the engine remake is still quite beta and buggy. I ended up playing the GoG version but maybe the situation has improved
- KeeperFX: Engine for Dungeon Keeper, adding 3D acceleration, higher resolutions, custom maps and working online. Also doesn't modifies any mechanics
- OpenRA: Command & Conquer, Red Alert and Dune 2000 game engines. If you have the original CDs can install the data and play the campaigns, else you have a free multiplayer or (highly difficult) CPU opponents. Probably one of the best of the list
- OpenTTD (Open Transport Tycoon Deluxe): Transport Tycoon was one of the best simulators I've ever played (alongside Sim City). Fixes some bugs and has working multiplayer
- OpenXcom: UFO: Enemy Unknown (XCOM: UFO Defense in the USA) redefined the turn-based strategy games. The original had some nasty bugs and seems to be some customization support (but I just play the original campaign/mode)
- ScummVM: I couldn't pass without mentioning THE game engine remake, because it allows to run most Lucasarts titles (which include lovely classics like Monkey Island or Maniac Mansion) but also because it is so multi-platform that can be run almost from everywhere you can think about. I used to play it even in a Windows Mobile PDA :_)
- Syndicate Wars Port: Syndicate Wars was an ambitious follow up, and the software-based 3D engine was really cool back in the day. This engine, while has the multiplayer part broken, allows to play with any recent OS
- Tenebrae: Quake engine to provide great 3D features but leaving the base game untouched. For a true enhanced experience, try Nehahra Project, which adds crazy stuff like bump mapping and provides also tons of new maps, enemies and even a 4 hours "movie"
- Zandronum: Multiplayer ZDoom mod for Doom, which means "tons of tweaks and optimizations". Itself allows to play Doom in high-resolution, but if you combine it with Brutal Doom mod you get one of the most insanely fun shooters I've ever played
I probably have missed some others, but I think with all excepting FreeSynd I have finished the full campaign/history at least once so they indeed work.
Note #1: Back in 2006 I wrote a similar post about Freeware and opensource classic remakes, you might want to check it out as has different ones.
Note #2: At October 2017 I found the incredible resource Open Source Game Clones with a huuuge list of opensource game clones, engine remakes and the like.