First thing I should warn readers here is that there is a major difference between playing this version of Guitar Hero: World Tour on the PS3 emulating the PS2 and an actual PS2. Try the PS2 version on a PS3 and you'll get pretty bad lag issues and even a glitch that will lock up the game and require a restart if you try to go into the Recording Studio with a microphone plugged in. On an actual PS2, these problems disappear and you actually get less lag in the Recording Studio than if you were playing the PS3 version.
Guitar Hero: World Tour for the PS2 is, for the most part, very similar to the PS3 or Xbox 360 versions, but with limitations caused by the lack of a hard drive or online support. Right off the bat, this means that you don't get online gameplay modes. Also, you don't get any downloadable content, one of the features that made Guitar Hero: World Tour's rival game, Rock Band, appeal to so many people. This is a larger issue than it might seem at first. The lack of this feature changes this game from a constantly evolving game with the ability to keep itself fresh to a one-shot game with a limited list of songs. This feature is sort of a big deal.
Another effect caused by the lack of online functionality is that you can't share your custom-created songs with others as easily. You could probably copy them to a friend's memory card or use a third-party device to upload them to a website, if you have one, but the PS2 version of Guitar Hero: World Tour is not going to give you a satisfying social experience. You've been warned.
All things considered, that might not be that bad a thing, anyway, since the Recording Studio is much more limited on the PS2 than on the other systems, mainly in lessened sound quality, which means you are much less likely to want others to hear your songs. This is sad, since the Recording Studio in the PS2 version of Guitar Hero: World Tour actually has much fewer lag issues than I saw in the PS3 version.
Aside from issues due to storage space and internet access, the PS2 version of Guitar Hero: World Tour has most of the same features as its more powerful versions. There is, of course, the Career mode, in which select an avatar or create your own, then work your way through the various gigs, improving your skill on an instrument and upping your difficulty as you go.
For those who just want to jump in and play, there is QuickPlay mode, which lets you simply select a song from any that have been unlocked already and any custom songs that you have saved.
If you're looking for some old-school, one-on-one dueling action, Head to Head is the mode for you. You can challenge a friend to a contest of musical skillz and see who is the better player.
The Rock Star Creator isn't really a gameplay mode in and of itself, but it is accessible from the main menu, as well as inside the game. This allows you to create different characters outside of playing the game, which can be nice if you're setting up characters for friends coming over for a party or a similar situation where you want characters created before the game is played, rather than having a long setup period before the game gets going.