Voltron, but that was before I knew Anime was a thing. Sailor Moon as well, because it would air before DBZ, and missing the beginning of DBZ was an awful thing back then iirc.
Probably Cardcaptor Sakura. Then years later I watched the sub and it really does make me wonder why they even bothered with the dub in the first place.
I watched Pokemon, dragonball Z and digimon when i was little, cant remember which one first. But in the case of watching fansubed anime on a computer my first was love hina.