I do like Lethal Weapon but I can also understand why it fails to live up to people's expectations. It's very indicative of the time of its release, which may also explain why watching it for the first time in 2015 may make it feel a bit off. On the other hand, the second one is a blast so if you ever feel like revisiting those two characters along with some really nasty South African baddies and a hilarious Joe Pesci, seek it out.
Big Trouble in Little China is my second favourite movie of all time and is just so much fun it physically hurts when I watch it due to extreme laughter. I'm positive I've seen it more than 100 times and it just never gets old. Russell as the stumbling, bumbling hero is great as you say and I've always loved that his sidekick basically became the real hero of the picture. Also, David Lo Pan totally rules. That is all.
Another one that I just thought of that you may like (if it's on there) is Three O'Clock High. Just watched it the other day and found it held up really, really well.