Before Sherlock there was a curly haired, socially awkward, big coat wearing British detective and for most of his run, Jonathan Creek was a brilliantly compelling and ingenius detective show. (Let's forget about season 5 and the awlfully written Polly).
Jonathan Creek differs from a lot of 'whodunnit' type crime dramas as it focuses more on HOW a crime/conundrum was done rather than who did it, which makes for some interesting cases and great writing to slowly reveal how a crime was done. Jonathan's out-of-the-box style thinking comes from small clues and piecing them together slowly, without telling anyone how it's done, until the big 'explaining' conclusion - which keeps you guessing as well as keeping the pace of episodes even.
Jonathan has a range of 'assistants' (similar to Doctor Who) who help him solve cases over the shows course, but really the best was his crime writer friend Maddy, who provides the perfect balance of sarcasm, humour and helpful advice. The show's earlier seasons also had great subplots including the ongoing book deals/writing Maddy does, Jonathan's career as a magician's trick inventor and the ongoing romancing of Adam and any attractive lady.
The puzzles and locked room mysteries varied hugely and it was always a challenge to work out exactly how they were done and sometimes even who commited the crime was hard to guess too. But the audience is never treated as if they are stupid or can't follow Jonathan's deducations and everything is always explained at a good pace with ample time to process how clever the puzzle and it's solution are (I'm looking at you Sherlock), giving a wider appreciation of stage magicians and sleight of hand tricks. Goodness knows how the writers come up with some of these puzzles *takes hat off*
All in all, the show sould really have ended around 2010, with the Christmas Special 'The Judas Tree', any episodes after that are far more flaky and poorly written. But even with the series dwindling in qualiy, the majority of the show is well scripted, nicely paced and inherently British, providing me with many evenings worth of high quality, if gentle, detective entertainment.