One thing I hate is the rap and hip-hop songs glorifying violence and disrespect and stuff like that. I also don't like the songs that are nothing but cusswords with some normal words thrown in. But don't worry. I'm quite aware that's not all rap/hip-hop songs, and may very well be a minority.
What I don't like about the genre, though, is the lack of melody/music. Some rap (note I said some, NOT all) is basically a sample of an older song with a more intricate, though computer-produced, beat and a poem laid down on top of it. To me, that just isn't enough.
First off, as a guitarist, I need guitar in my music, at least most of the time... and occasionally I'd like to hear a guitar solo... I mean a real guitar solo (Jimmy Page, Jeff Beck, Stevie Ray Vaughn, Carlos Santana, David Gilmore, Eric Clapton), not a 4-measure "bridge" that we like to call solos these days. I also need more instruments and more music.
I don't like how some of it is computer-produced as well. Computers canNOT write good music. Period. The MTV/VH1/Clear Channel-era has proven this over and over again, and it is one major reason I can't STAND modern-day top-40. Music should be written by people, and only people, and it shouldn't be constrained by radio time-limits and shit like that.
I also like emotion and meaning in my lyrics. Don't get me wrong... I love songs like "Whole Lotta Love," "Anything Goes" (G'N'R), etc for their... well... their fun songs. But I'll pop in "Time," "Since I've Been Loving You," etc before I pop in any "fun" song. I like deep lyrics... that said, I'm not a fan of artists who inject politics in their music (although, oddly enough, I find myself a fan of Roger Waters, John Lennon, Bob Marley, Bob Dylan, and other "political artists"... I though I generally steer clear of their heavily-political songs, with the exception of "Imagine," which is a song I love).
On that note, I have heard some musical, emotional, deep rap/hip-hop songs that have intrigued me... I even heard a rap song with an incredible guitar solo (and no, it was not Rage Against the Machine, though I am a fan) and yet I find that these songs are no where near as popular as the throw-away fad-crap MTV likes to make famous.
So while I realize that, like all genres, no two rap/hip-hop songs are alike, the genres have their good songs and their bad songs. Unfortunately, it's the bad songs that MTV, VH1, and Clear Channel like to make famous, and the good songs that stay in relative obscurity (for the most part).