dang tough decision to make tbh.
loved all the adventures from Lucasarts of course. Recently I dug out "the Dig" and played a while. It's a tough game.
The first Lucasarts Adventure I've played was Maniac Mansion/monochrom/english. Still remember as I was looking for the chainsaw-fuel
but to make a list:
1. Indiana Jones 4 (waited months for it while playing the demo

)
2. Monkey Island1/2
3. DOTT
4. Zak McKracken
5. Sam 'n Max (recently played Season 2 but... it's not the same)
but 1-5 who carez? I could mix them all up randomly and still would be satisfied whats on place one to five.
also good games imo were the Riddle of Master Lu and Baphomets Curse. (but both aren't in my top 5

)