I too grew up with the 80s TVB adaptations, and when I saw the 90s adaptations, they felt threadbare and sterile by comparison. By the late 90s though, my self-taught written Chinese had gotten to the point where I could read entire Jinyong novels without constantly referring to a dictionary, and I have never looked back since.
It was startling to see just how different the novels were from the 80s adaptations. In addition to the addition of tons of filler material, the very personalities of the characters were markedly different. One common tendency was to focus on some aspect of a character's personality or relationships, then blow that completely out of proportion while neglecting the others - e.g. Huang Rong's mischievousness, Zhou Botong's childishness, Wei Xiaobao's friendship with Kangxi, Yang Guo's friendship with Yelu Qi, Guo Jing's relationship with Genghis Khan etc.
For example, I cannot picture the novel Huang Rong doing any of the following:
- Stripping Hong Qigong naked (except for his underpants, obviously), tying him up to a stake on the beach and letting the tide come in
- Hanging Guo Jing upside-down from a tree on a rope for a whole day, then dropping him down to the ground after he fell asleep
- Slapping Guo Jing and threatening to kill him with a dagger after hearing about his relationship with Hua Zheng
Another example is that the relationship of Tony Leung's Wei Xiaobao with Andy Lau's Kangxi was far too casual. For example, near the beginning, you had Kangxi taking out his frustrations with Oboi on Wei Xiaobao to the point of spitting blood, then Kangxi gasping in horror, profusely apologising to WXB and whining about what a nasty man Oboi was (in that tone of voice). Later on, you had the two casually conversing and gradually changing positions, until WXB was draped casually on Kangxi's throne. The novel WXB would never dare do that in a million years!
I've written at some length before about the differences between novel and Andy Lau's Yang Guo, so I won't go there again. In a nutshell, I find the adolescent novel YG somewhat arrogant and aloof, whereas Andy Lau's was gregarious and... smarmy perhaps? Little Dragon Girl also seemed more aggressive and sure in her relationship with YG - e.g. in ROCH '83, she moved as if to kill YG when he said he couldn't take her as his wife immediately after the rape, and later on when she overheard YG saying that he was going to marry Guo Fu to the Wu brothers, she didn't believe it at all.
Aside from personalities, some events were reversed for some reason. e.g. in the novel, Zhou Botong was prevented from leaving by Huang Yaoshi, while in LOCH '82, it was ZBT refusing to leave and HYS trying to get rid of him. Or in the contest for HR's hand, the adaptation had Guo Jing lose the first contest (because ZBT helped him), and win the second one (which was a pure inner strength contest).
While there were an excess of additions to the 80's series, there were also a few curious omissions. The 2 pet eagles never appeared at all (except maybe at the beginning of ROCH '83, but it wasn't clear if they belonged to the Guos), and they made the giant condor fly instead. This meant that the death of the 2 eagles was missing, which was a great opportunity to really drive the 'Ask the world, what is love?' poem home.
A lot of these differences may seem trivial, but they have a big impact on the overall tone of the story, even if the overall direction of the plot is the same. Jinyong's novels tend to be more character-driven compared to those of his peers (which tend more towards being event-driven), with the later novels even more so, and proceed at a relatively sedate pace, going into great explicit detail about the characters' thoughts, motivations, strategies, interactions etc. By modifying or not showing such a major aspect of the novels, it often feels like the very essence of the story has been altered.
These things do tend to be rather hard to portray on television though. I do feel that the portrayal of characters in the 90s was more accurate by far (HSDS and Flying Fox excepted), but due to the limitations of the medium, most of the subtleties didn't come across and you end up with a skeleton of a story, stripped of most of the original meat from Jinyong. The 80s by contrast had a much larger skeleton with big chunks of the original meat replaced with lots of synthetic meat from the TVB scriptwriters.