I see what you're trying to say, but I hardly think that SWGB had a comparable level of detail to EaW.
Detail, when used so generally, can refer to several different things, so I've ran through a short list.
Graphically EaW is superior, so you can't really make the arguement that SWGB had more detailed graphics (the laser blasts in SWGB for instance, were hand drawn, whereas in EaW it's quite clear that an in-game particle effects engine generates them). The polygon counts on ships, facilities, and troops are incredibly higher then what SWGB could offer, and the explosions and effects are several levels beyond the best that SWGB could bring to bear.
What about the attention to detail aspect of both games? SWGB did a fairly good job of portraying each side's EU units accurately, there were some inconsistencies, sure, but for a game based solely on land combat, it did a pretty good job of adhering to strict canon standards -- but it was nowhere as encompassing as Empire at War is in the whole.
For one, Empire at War incorporates both land and space, and space is a huge element to Star Wars (hence the title). There's nothing quite like the feeling of commanding a fleet of Star Destroyers and watching them enter a system, foreshadowing the ensuing destruction to come. And unfortunately, SWGB doesn't offer that (the ISD hack simply put a cruiser on the game with an ISD model, not that impressive). There are tons of different unit types for each side (although certain ships like the Loronar-class Strike Cruiser, and Lancer frigate are missing from the Empire), and in-general, there's a good deal of attention paid to canon detail. I mean, Mon Calamari cruisers are able to boost their shields, and in the EU, they are notorious for powerful shielding.
But again, that's mildly off subject, because SWGB really didn't have a space game to compare to, so one has to look at the ground game. Well, the ground game is phenomenally better in EaW. I don't recall any maps on SWGB were the terrain actually affected your troops (save mountains and water), on EaW, fighting in the midst of a sandstorm on Tatooine actually kills your accuracy. Additionally, SWGB hardly accounted for the various lifeforms inhabiting each planet -- sure they had Jawas, and the occasional wild beast, but have you seen Rancors in EaW? There's just a bigger sense of detail.
Additionally, each unit is fleshed out more, you can take cover, you can deploy troops from an AT-AT, you can call in powerful airstrikes. You can call in for reinforcements from your space based forces, you can build structures if you have access to building pads, there's just a ton to do and it's all grounded in Star Wars.
I mean really, ask yourself, what game is the most detailed? I'd say quite easily it's Empire at War.