I have been to Vegas 4 times and I'm not 21 yet. I have been in every single themed hotel on the strip. My advice, if you want to have more money to spend on gambling, and other stuff stay in a hotel off the strip its much cheaper and they arent horribly bad.

The shows there are amazing. You have to go to a show in Vegas.

Hotels to avoid are Circus Circus, unless you check out the theme park there but its nothing spectacular, and Excalibur (I think thats what its called) its the castle looking one. The only good thing about Excalibur is the dinner show they put on but thats more for the kids.

Have Fun and Dont lose all of your money

the "peppermill" is another decent hotel/casino to try if you're visiting on the cheap. it's also one of the cleaner places out there, and it's relatively closer to the strip than the other smaller hotels. the slot machines aren't as loose, however.