A True Classic
This is the "Spartacus" or "Ben Hur" of RTS games - vastly superior not only to its contemporaries, but to the more recent additions to its genre as well. Newer Total War titles have "improved" on this title's graphics and options, but they've never matched the perfect balance between large-scale strategy and unit-by-unit tactical simulation of Rome. This isn't a dense, empire building, mechanics-heavy Crusader Kings II-style strategy game, and it's not a mindless go-go-go unit-spamming RTS; it's something between the two, and it occupies that niche with the dominance of a Roman garrison.
The flaws of the game are worth mentioning, if only for completeness. The "diplomacy" system is as useless as Roman cavalry. The historical accuracy is questionable at best (the three Roman factions are an invention of the designers, for example). And the game becomes a bit of a grind in its middle stages as one's faction expands.
But these are all minor problems. Are you really looking for good diplomacy in a game called Total War? Historical accuracy is great for documentaries, but I want some War Elephants in my Gallic horde, thank you very much. And if you find yourself complaining about the difficulty of defending and expanding a vast, sweeping empire, isn't that a pretty good problem to have?