It's hard to compare, since the games are being designed by totally different companies with no code being shared between the projects.
Moo1 had...adequate AI, I guess. The ship design was intelligent, the AI would build various types of fleets and would design ships based on what techs/tendencies you had, IIRC. As almost all empire building AIs go, it didn't prioritize highly for industry/research, so it'd often lag far behind. It did not take advantage strategically aside from the most basic chores, such as leaving an undefended colony near their border.
Moo2 was possibly worse in the AI department. The AI ships were horribly built and could easily be outclassed. The AI using the ships was, for the most part, vaguely decent but has exploitable tendencies. Planetary management AI is just plain dumb. Diplomacy was usually pretty bone-headed as well. Strategically, the MOO2 AI was an encephaletic, still born infant, who would often declare war when seeing one lone outpost it could blow up, even though you outclassed it in every single way.
Moo3 appears to be much better on a tactical and strategic level. There's indications that the AI will figure out your tendencies and build counter-mission ships to defeat you. It'll definitely use the ships correctly, and appears to do a good job managing weapons on those ships. It appears to do well on the tech tree. It might not be so great with industry buildup; hard to say, really. It does appear to be reasonably smart when declaring war and attempting to do realistic goals without totally irrational behavior. It appears to be pretty reasonable on prioritizing expansion over consolidation. Also appears to be quite decent at spying and diplomacy, especially in the senate.
It looks like it'll be better than something like, say, Civ 3. Honestly, only folks that really could tell you would be the beta testers.