Most definitely one of my bigest gaming loves.
And that is more then well deserved position! OW is (even thought it´s age) original not just in the means of timetravel and war in the far past and for the past. Above all it´s brilliant combination of rts and rpg, what makes it so unique. In terms of gameplay it means you have to care about every soldier you have (and in this harsh environment, it´s usually much less than optimal numbuer). You have to always think abut for what to use each soul and how to treat it. What skills to train, where to allocate the manpower, what technology develop and when. Becouse even won battle for valuable resource, if it took too much time, can endanger development of your base and therefore whole mission. Loosing any soldier means hell of a trouble. There are usually multiple ways how to achieve your goals, but every one need careful tactical thinking from base management to field battle strategy.
This way it may sound like hardcore stuff for very patient tacticians... but it´s not. Above all, it´s very enjoyable game for anybody. The main experience isn´t frustration, but fun. Lots of fun. There are some things that help this outcome. First is excellent level design. Missions arent repetitive, but almost always bring some new challenge. They vary from more traditional base-to-base war to Commandos-like stealth action. Often there are also twists in the developement of events, which boosts gameplay with dynamics and pushes you to be prepared for anything.
The last but not least quality is the main story. From the "cliché" of American-Russian war (just situated in unorthodox setting), situation quickly extends to be more complicated. Player is therefore forced to choose which side (and which politcs, ethics and philosophy) to pledge allegience to. Not just from global perspective, but from personal view of main hero and his relationships, too. Which even adds emotinal touch to game. Quite special for rts, isn´t it? Oh, I forgot to mention that (living) soldiers and their valuable experience goes to next missions. And that for some of the more important characters amongst them, you will soon develop special feeling.
Game has, of course, it´s weaknesses (like poor voicecast), but there are not many of them. Somebody may despise the old graphics, but I like it even after all those years.
So in the end I have only one advice regarding Original War: Enjoy It!!!