I agree with SuspectimusPrime. RiD is also decent... it's aimed at a very young audience, but it's reasonably good considering. Although RiD cuts stuff out from Car Robot, but obviously RiD is more accessible if you don't speak Japanese.

Beast Wars II and Beast Wars Neo are just poor, and I wouldn't recommend them. If you just want a taste of them, I'd recommend watching the Beast Wars movie (Lio Convoy in Imminent Danger - this movie also expands on the Canadian Beast Wars series), and the final story arc of Beast Wars Neo (i.e. the Unicron arc). The rest of those series are quite forgettable.

Zone is worth watching IMO. It's really well animated, and while the story's not flash, it's just cool seeing all those Micromasters in action. The one Japanese G1 story I would recommend avoiding would be Scramble City. *shudder* It's just terrible... not even worth watching for their attempt at filling in a continuity hole (i.e. the construction of Autobot City). Maybe just watch the very beginning where you can see Autobot City being built, then just stop watching after that. Rescue Bots is aimed at infants... there's no real appeal to it for adults. I wouldn't recommend watching it unless you're supervising little kids. Having said that... it's better than Go! Go! Go-Bots (aka Transformers Big Adventures). Rescue Bots still retains the "robots in disguise" motif and I'd rather see the Transformers trying to rescue and help people rather than trying to 'correct naughty robots' (guuugh! ). And Rescue Bots does actually try to have some form of character development... not great, but arguably better than Michael Bay.

As for the Unicron Trilogy... the dubbing in Armada is horrible and it really kills some of the feel of Micron Legend. Especially the way that the Autobots were portrayed, all effectively sounding the same, whereas in Micron Legend they all sound distinctly different. I also felt that Armada Starscream was just annoying, whereas he's actually a really noble and admirable character in Micron Legend -- a character one could emotionally invest in. After my disappointment with the dubbing in Armada, I didn't bother watching the Energon or Cybertron dubs, so I only watched Super Link and Galaxy Force. Super Link is actually reasonably good - there are moments of the story that get really heavy with serious deep and meaningful stuff (one scene even discussing the meaning of life!). I have no idea how well this was translated in Energon though. Galaxy Force I find not so good though. :/ Some great toys, but yeah... series fails to really engage me.