Primeval is definitely this show for me. When it first started it was honestly one of the best shows I'd ever see. It was such a creative story line with incredible characters and great action scenes abound. The show perfectly balanced the drama within the character's lives and relationships with the importance of the monsters they were stopping and the overall 'main goals' of the show and the main 'bad guys' had a ridiculous level of charm to them. The show threw out plot-twist after plot-twist whilst all the while remaining the same excellent show, even showing that they had no problem with killing off main characters to keep things, however this is where the downfall begins.
Once they'd killed off one of the main group it was wonderful because, despite him being one of my favourite characters (and v cute!), it was exciting to know they'd go to these lengths. Next they decided to kill off the main character of the entire show. This was not such a good move, the show took a dramatic downfall after he left and it never quite reached that level of excellence again. He was replaced and the replacement was good, until once again he died. This was starting to get grating but the show still remained watchable. Then came Series 4. Series 4 came along with the introduction of a host of new faces to the team leaving only two of the original team (and their boss) remaining with a swarm of new characters completely stealing their focus. Honestly at this point it just felt like an entirely new show and I gave it a chance, but it just wasn't for me any more. They then decided to make country-specific versions (the latest one is Canada, I think!) which is just... why.
tl;dr that show with dinosaurs