For me it’s The Brother’s Grimm. 38%/39% tomatometer/audience respectively.
I also agree with Hansel and Gretel and Speed Racer.
Just thought of this one. Paycheck (2003). Based on a Philip K. Dick story as if you couldn’t tell. I’ve got a bunch more but they are all pre 21st century.
Actually, Transcendence (2014). An old reliable sci-fi plot is likeable schlub gets superpowers, becomes insufferable jerk, saves world, is still insufferable. In this movie likeable adept man get superpowers and stays likeable. Everybody else loses their damn minds and try to kill him. World is not saved. (Or is it?) (Contains graphic scene of keyboard used as doorstop)
Unfortunately North is too old (1994) to qualify. I did enjoy Year One, though.
Only God Forgives (2013). 41% on the tomatomater and 37% with viewers. It’s a bleak arthouse film with lots of violence and other nastiness so it’s certainly not for everyone, but it worked for me.
Constantine (2005) and Conan the Barbarian (2011) for me.
Power Rangers (2017) is at exactly 50%, which may or may not count.
Jay & Silent Bob’s Super Groovy Cartoon Movie is unrated by RT critics, but has a 24% viewer rating, and I loved that flick, so I’m gonna count it.
Hell, yeah! The actors playing soldiers actually moved like soldiers, with proper military tactics, all while they’re fighting bug-eyed monsters. What’s not to like?
Hulk (2003) has a score of 62% with critics and 29% with audience so I am not sure it qualifies. But I really enjoyed it and though people are under-rating it.
Terminator Genisys (2015) has a score of 26% with critics and 53% with audience and it’s another movie I really enjoyed. I can understand how it might not be everyone’s cup of tea. Time travel movies have a tendency to be overly-complicated and this is a prime example. Also if you haven’t seen the first Terminator you might a little lost watching it.
That was going to be mine.
But as a unique pick, one I still don’t understand the hate for: Cars 2.
I thought the Andam Sandblerg movie “That’s My Boy” (20% fresh) was quite funny.
This is another good one. I genuinely really liked that movie.
I could only find one that counts for me, Lara Croft: Tomb Raider (2001). It wasn’t great cinema by any measure, but it was fairly enjoyable to watch once.
I’ve always liked ‘Starship Troopers’ (looks around defiantly) with Neil Patrick Harris, Casper Van Dien, and ex-Mrs. Charlie Sheen, Denise Richardson (piloting a spaceship). Shooting and blasting CGI ‘bugs’ - do you want to know more?
Justice league. the Supe was poor, the rest were fine.
John Carter. Could have been better, but not bad.
National Treasure - actually very good.
Of the three, National Treasure certainly doesnt deserve its low rating, but perhaps it’s sequel does. It really makes little sense to have the FBI chasing him since the President could have explained it.
Psst, salinqmind, that film was released prior to 2000.
Damn right, so unappreciated.
Well, if it wasn’t for the 2000 cutoff I’d mention Cherry 2000. 40% at RT (and 1-1 among top critics). 
2000
I actually, really** liked** 2009’s Outlander, with Jim Cavaziel. I checked and it had a rating of 37%.
I was sure I would be able to go with the first movie that popped into my head. Who knew Mother! (69% at RT) was understood and enjoyed by so many?
So I’ll go with the second movie that occurred to me- Den of Thieves (41%) an underrated heist movie with a nice twist.
DrDeth, I was going to mention John Carter, but it turns out it’s over 50% on both scores. It was a flop, sure, but those who saw it still mostly liked it.
I’ll second “Year One.” It’s funny little vignettes. Yeah, it’s crass and a bit shoddy - but that’s comedy, amiri? And Jack Black’s response to “the holiest of holies” is gold.
I’ll add 2001’s “Joe Dirt” - polling among critics at a dismal 11%. But I think it’s funny, and even more than that - had enough actual heart to make it work. Lovable loser sort of thing but it really does get you rooting for Joe. My favorite part is how he never quite lets anything get him down - even though by all means he should. I love the scene where he can’t believe the fireworks stand is only selling snakes and sparklers. I also thought Kid Rock turned in a good performance - I know people like that and it rang true.
I believe I may have been waiting 18 years to talk that much about Joe Dirt… 
Red Sparrow (45/49 on Rotten Tomatoes). I thought it was terrific, and the bad reviews mystify me. I bought the DVD, and I even read the Red Sparrow novels (there are three of them).
I enjoyed The Canyons, a notorious Lindsay Lohan vehicle (22/15 on RT). I put off watching it for years because I heard it was horrible, but I found it compelling and very solid.
I also like some of the other movies mentioned in this thread—Terminator 3, The Lone Ranger, Hulk, Constantine. Terminator Genisys wasn’t bad either.