LOL the quality and plot of the movies have declined ever since the 10th one or so.
Also if you watch them one after another you can see the change in art style and Ai's hair color xD
The 5th movie remains my favorite, countdown to heaven. Man I LOVE when Conan drove the car literally flied from A tower to B tower.
The 10th film has a very interesting plot.
The 13th movie, to be honest, if it weren't for the Black Organization it wouldn't be that interesting at all.
I mean, Conan is getting closed. He found out the identity of Bourbon (an intelligent man from the organization; love Sherlock Holmes and his deductive skills are great). Manga chapters 815 on (I think) is about their showdown.
There are some TV specials which feature 1 hr long episode. Some of them are awesome. Here is a few that I recommend:
128 and 129 (2 hr) - Ai's first appearance and her sister being killed
162- Shinichi's first case
174- 20 yr old murder case; not as interesting as other but still good; 2hr
176-178: meeting with the organization again; Piscol showup and Ai returned to her original form for the first time and getting shot and injured; Piscol killed RECOMMENDED (Referenced in 13th film too)
187-193: Conan hurt in the woods and he returned to Shichini because Ran was getting suspicious and solved a case in his high school; RECOMMENDED (referenced in 13th movie and a bunch of other episodes and chapters)
219: 2 hr; I HIGHLY RECOMMEND THIS ONE; this remains one of my FAVORITE! it's FANTASTIC!!!!!
263: 2hr; I just love seeing Hattori and Conan working together.
286-288: Ran's flashback; Shinichi's case after he got off the plane (since 162 lol); first appearance of Vermouth
304: I will BOLD THIS EPISODE; this is one of THE BEST EPISODES. A MUST WATCH!! 2hr
309-311: contact with the Black Organization
345: again I will BOLD THIS; showdown with the Black Organization; this is been referenced a lot later on; important episode
356: 1hr; showdown between Kid and Conan
383: Hattori + Conan; 2hr
394-396: Kid vs Conan vs Detective Boys
425: 2.5 hr; HIGHLY RECOMMENDED; referenced a lot in the future; key to future plot
463-465: black organization
469-470: kaito kid
472-473: Shichini as a child meets the original Kaito Kid, who is the father of the current one; these two episodes explained why Kid later called him a brother; (because apparently the original Kaito kid is the teacher of Shichini's mother and Vermouth)
479: Hattori + Conan; LOVE IT
490: Hattori + Shinichi from middle school
491-504: Aki and Black Organization; A.MUST.WATCH!!
515: Kaito Kid
516-517: two very nice episodes
521-523: Ran getting close to Conan's true identity
558-561: I love these episodes
616-621: Conan in England lol; confessed to Ran
That was a long list haha
Hope you enjoy some of it