I never liked any of the Gundams except the original... In the first ones the Gundams were at least within the realms of possibility, then they threw that out the fucking window as soon as they got into the other series.
Some of the OAVs based on the original series keep things more realistic. I liked Stardust Memories, myself (it has a great "everybody loses" ending) and War in the Pocket never blows anything out of proportion. You really get the impression that a single Zaku piloted by the right person could take down a Gundam.