In terms of overall engineering and construction, I'd say today's Transformers are better made than G1. Consider the following:
(1) Contemporary Transformers are far better articulated & pose-able than G1 Transformers.
(2) Contemporary Transformers are more durable than G1 Transformers. Just earlier this evening I was playing with RtS Special Ops Jazz at a playground where I had him hanging off a net at a height of about 1.65m... then this little girl bumped it and he fell smack on the floor below. The toy's still fine. If that'd been 1984 G1 Jazz I don't think it would've fared so well.
(3) Contemporary Transformers have more detailed sculpting and detailing. The idea of using stickers to add details seems crude by comparison.
Now I'm not saying that G1 toys are bad... they generally were very well engineered for their time. However HasTak have come a long way in the last 27 years.
I personally never saw Transformers being sold in newsagents. Although newsagents were a vital source for me in obtaining TF comic books as I didn't discover comic book stores until the 1990s.
I don't think having Devastator in complete green would look that good. IMO Devastator's Diaclone colours looked better and I prefer the more realistic and varied colours of ROTF Devastator. The more simian stance is something that occurred due to consideration to laws of physics. A robot that size and immense mass standing completely erect like a human would make it more cumbersome to stand and move - particularly with any ferocity for fighting.
My gripe with the Constructicons is:
+ No character development. They were treated like set pieces rather than characters.
+ Killed by off-screen human cannon. Yeah, I know it's plausible, but I would've liked to see the Autobots take him out.
The original 1986 Transformers The Movie was a box office flop. While Transformer fans like us love it, general audiences didn't and critics gave it scathing reviews. Think of it this way - if you knew nothing about Transformers, Transformers The Movie is not a terribly engaging movie. One of the great things about the first live action movie was that anyone could get into it, and lot of people enjoyed it, not just Transformer fans.
I agree that ROTF was weaker than the first movie though. ROTF had some good moments, but also some bad moments... it was a rather "bipolar" movie jumping from hot and cold. Hopefully Dark of the Moon will be better (couldn't be possibly worse, right?)