I think that most people bashing on C&C3 and RA3 do it simply because it relates to Electronic Arts, but they probably don't realize anymore that Westwood Studios' (the original developers of the series) first mistake was recognized back then to be Yuri's Revenge, the expansion pack to the beloved Red Alert 2, and I agreed back then as well, no one really wanted a third "race" to be implemented, until then Red Alert had always been a conflict between the Allied and Soviet forces, and then comes in the very first WS' attempt at milking the franchise for no real purposes other than to screw up most of the original RA2's balance which was generally fine before Yuri came in.
But I understand that nostalgia probably helps in keeping the "old" C&C titles on a silver platter rather than analyzing them for what they really were. I guess in that end however that it comes down to subjective views entirely. I for one liked all of the C&C games including Yuri's Revenge despite its issues, but obviously some are better than others, but I do not "hate" a single one of them. I really liked C&C 3's single-player campaign and I thought that the campaign from Kane's Wrath (expansion pack to C&C3) was even better since we went back in time a little bit during the Tiberian Sun (A.K.A C&C2) time line, which for me was a really pleasant surprise because C&C2 had the best events occurring of all the Tiberium saga, although I do still like the original C&C very much (probably due to the music score however, which to this day is still brilliant and so enjoyable to listen to).
As for RA3 I liked it. It could have been better, of course, but I thought that Yuri's Revenge was worst, although RA3 could be seen as a glorified Yuri's Revenge (three factions battling it out instead of the original Allied Vs. Soviets context). It retained its intended cheesy acting, which I thought was very well done and was very much reminiscent to Red Alert 2's cut-scenes, the music fits in very well, especially the main theme which simply kicks some major ass (especially considering that the music in C&C3, in general, isn't good, in my opinion anyway).
But, overall, I liked them all really, my absolute favorite within the Red Alert time line is Red Alert: Retaliation (from the original time line, before the sequel) and C&C 2 (both Tiberian Sun and Firestorm) for the Tiberium saga (with Kane and the Brotherhood of Nod). I think that if there's a franchise that managed to live to this day that retained pretty much the essential without being screwed too much it has to be C&C despite being maintained and developed by a company that most people including myself love to hate, but I tend to give credits where due, I'd rather see a financially capable company trying to keep C&C alive than seeing the franchise falling under poor hands and not being able to resume it at all.