An absolute classic.
If you can get past it's outdated graphics, gameplay quirks and all that, it's fast-paced early 2000s action is still enjoyable even today.
The single-player campaign is pretty good, though I don't really like the parts where you have to defend some sort of objective from the bad guys like the one with the bridge with the paratroopers in the British campaign but all in all it's a pretty good experience.
I never actually got into the multiplayer portion because I'm not really interested, because I have a lot of multiplayer games I would rather spend some time with, like Wolfenstein Enemy Territory, an amazing multiplayer spinoff of RTCW.
Though the game has showed it's age, it's definitely a must play if you can get pass it's outdated graphics and stuff. Setting it up in a modern W10 system is pretty easy, just grab a copy on steam and go! But if you wanna tweak the screen resolution and FOV, you're gonna have to do some fiddling with the game's config file, there are some tutorials that will help you with that.
The game has a pretty lengthy campaign about roughly 7 hours, much longer than recent installments in the franchise. But the United Offensive expansion pack will add some hours into that, it's an amazing expansion pack (think DLC) for the original game.
All in all, it's an awesome game that started a billion dollar franchise everyone knows and loves.