I practice tons of academic rhythm exercises: different strumming patterns, 8ths, 16ths, use the metronome.

But when it comes to actual music... I cannot figure out the rhythms to save my life. Can't hear anything complex or syncopated, no ability to count.

I spent about 6 hours trying to figure out the strumming pattern to Elvis' That's Alright Mama. Hardly rocket science. But there's something very subtly off I just can't get.

Is rhythm the kind of thing that you really need to work on for a long time, or is this gonna be rough for me?
Maybe you need to just feel it instead of count it.
Oh yeah.

Quote by hildesaw
A minor is the saddest of all keys.

EDIT: D minor is the saddest of all keys.
One thing I've found is that sometimes people try way too hard to capture the rhythm in what they're trying to play. I had this problem REALLY bad!! When I started playing I found out very quickly, at least from my perspective, that rhythm guitar is very difficult compared to playing melody for the exact same reasons you're experiencing. You just have to practice, practice, practice. You're going to get tired of hearing that but it's true. Eventually you will "pick up" your own technique for rhythm. Very few people play guitar the same way. This is what defines your style of playing and it will be unique to everyone else. It's just like strumming. Everyone does it differently. It has to be what works for you even if it's slightly technically incorrect. If it sounds good and you can stay in rhythm then that's what you need to do. Keep practicing!! That's about all I have. Good luck!!

Ibanez SGT520VS Sage Series Acoustic
Yamaha FG720S-12 12 String Acoustic
Schecter C-1 Classic
Crate Flexwave FW65 Combo Amp
You can do all the excersises in the world, but all it'll teach you is what each note length feels like.
Stuff like the strumming pattern that Elvis plays in that song can be tricky to keep going.

One solution is to never stop strumming with your right hand, and simply move your right hand away from the strings or mute with your left hand.
Call me Batman.