My biggest problem with todays themes, even the good ones like Miz's, is that most of them have absolutely nothing to do with the wrestlers who they're attributed to. Most, if not all, of todays themes are easily interchangable. Generic top 40 rock songs slapped onto some wrestler for his entrance theme.
I hate to say it, but only John Cena has music that is written specifically for him. Sheamus' is pretty good as well, seeing as how it has that celtic irish feel to it. But other than that, the rest are all interchangable.
Entrance music is important, just like a guy's ring attire, his hair ... everything that adds up to create a particular look or feel or theme. Look at Undertaker, everything matches, from the theme to the ring attire. He's a very specialised example, but you get my point.
Now, I'd disagree with MMK on the subject of
the Miz. The feel of the lyrics and all this 'I came to play' stuff reeks of school playground bully, and in many ways that's what Miz is. The kid who thinks he's it, when actually, he hasn't got a leg to stand on; that's the character that's been crafted out of the Miz for four years now.
Sheamus and Cena I'd definitely agree with MMK, but I disagree that they're the only ones. Sometimes you have to look further than 'These 30 wrestlers all come out to rock music'. Look at the lyrics, chords, feelings and atmosphere and you have 30 very different songs, even if they all exist within the same genre. Compare for example, Drew McIntyre's music with Dolph Ziggler's. They're both rock songs, but very different.
Also, sometimes it's not the genre so much as it is
musical motifs. Why do you think most wrestler entrance songs start with their catchphrase, or a recognizable sequence? Glass shattering, 'If You Smell...', the Y2J countdown/'Break the walls down!'. The fact that Triple H's Motorhead theme still uses the riffs from his 'Higher Brain Pattern' and 'My Time' themes is very important, and remember that when Big Show and Undertaker teamed in '99, you basically had a 6/8 version of the Ministry theme, with a baseline similar to Show's normal theme. All of the Rock's themes have used a similar rhythm and every one of them from '98 onward uses the same riff, usually in F (but the latest one is in E). Look at Natalya. In recent years, the basic structure of Bret Hart's changed from being Bret Hart's theme to being a theme for anyone who trained in the dungeon.
However, I'd say one guy who seriously needs a theme replacement is
Wade Barrett. The very first version of End of Days sounded like it fit him, it wasn't heavy sounding, but the newest one is quite grungy and heavy. Really, Wade needs a theme with more 'Brit-rock' feeling to it, but I wouldn't like them to just stick him with something classical-sounding. After all, he's not the same character as Regal.