Not sure what's all been dubbed honestly personally but from what I remember/know the dubbed Gundam anime are: The original simply titled Mobile Suit Gundam (sometimes called Gundam 0079 by fans), Gundam Zeta, 0083, 08th MS Team, G Gundam, Gundam Wing, Gundam SEED, Gundam SEED Destiny, Gundam 00, and Gundam Iron Blooded Orphans.
Out of these I'd recommend, Iron Blooded Orphans (newest series), 08th MS Team, 0083, and even the original. SEED and 00's second half are low points in what was otherwise a pretty excellent first half. Others will recommend Wing most likely as its where they started.