This a conflict for me, because I think both games are good and I'm a fan of the action/gta style and stragety games.
Now when putting it on the table, you have GTA3, the game that started and revolutionlised the new GTA style we all know and love (aside from a few good people), but it was still a few sugars short of a cup of coffee and didn't reach it's full potential until Vice City and San Andreas came. And you have Red Alert 2, one amazing stragety game, of which you could do so much with the Allied Forces and Red Stars, I think in my mind it's the best out of the series and I did enjoy Red Alert 3 too.
I think with this one, I might go against my stragety lovings and back GTA3, reason being is because it did create a gameplay style that alot of other games followed and I rememeber back when it first came out, it was the game everyone wanted to have the PS2, breaking the censor laws at the same time! I think both are great games but GTA3 did something to the gaming world that RA2 didn't manage to reach. I don't want to follow hype or anything, but alot of formats have been GTA clones because of number 3, is there anything that spun off Red Alert 2? Not that I can think of aside from the sequel, it was a great unqiue stragety game, but alot of games came before it, like Red Alert One.
GTA3 on this one.