Do you fancy revisiting the original Red Alert and Dune 2000 with a few minor improvements and tweaks? OpenRA may be just what you’re looking for.
OpenRA is a fan-made, open-source engine specifically designed to play Westwood’s vintage titles. You don’t need to struggle to get them to run on modern OSes and you don’t even need the original discs. The engine automatically provides the needed files and runs natively in Windows, OS X and even various Linux distros.
Though gameplay remains largely untouched, there are a few options to smooth things over and bring the titles closer to modern RTSes. These include experience earned by units, the ability to choose between left- and right-clicking and the ever-classic fog of war. On the technical side of things, it features modern networking code and support for today’s insanely high resolutions.
Options for both multiplayer and AI skirmishes are present. You can grab the goods at the project’s official page. In addition to the aforementioned Red Alert and Dune 2000, the engine also supports Tiberian Dawn with Tiberian Sun currently in development. As an extension of its nature, OpenRA can also be used as a general purpose RTS engine with extensive modding capabilities: a number of non-Westwood mods have already been developed, which you can download from Mod DB.