With “Rock Band 2” having been on the market for a couple of months, the conventional wisdom has been established: It’s more like “Rock Band 1.5” than a true sequel to last year’s acclaimed series starter. But that thought just isn’t fair. Sure, the sequel to “Rock Band” doesn’t include anything as game-changing and ambitious as competitor “Guitar Hero: World Tour’s” par-baked song-creation mode, but what is there is perfectly tuned and plenty of fun.

As in the first “Rock Band,” you and three friends sing, drum and play a pair of guitar controllers along with licensed music tracks. That core package hasn’t changed, but it does come wrapped in an exquisite new package, as developer Harmonix has isolated and improved upon the first game’s weakest areas.

For starters, the setlist-style, “play five songs to unlock five more” song structure in the single-player game has been ditched for an experience closer to what you’ll get in multiplayer. You’ll create a rocker (in my case, Wile E. Peyote), add him to a band (Peyote Ugly) and send him out to the world’s cities. As you play through the game you’ll earn fans and money, win a van, sign a record deal, make music videos and hire staff. This arching fiction, while not strongly written, drives the game forward in a way that’ll keep you coming back for more.

Harmonix also made a number of tweaks to online play. Last time out, you could play “Rock Band” with your buddies online, but your fun was limited to playing individual songs outside of any of the trappings of a real-life tour. If you wanted to play Battle of the Vans for the right to win a beat-up old minivan, you could only do it by inviting your friends over and having a go. You’ll be pleased to know that in “Rock Band 2,” you can form a whole band online, which makes it great for those of us with far-flung gaming buddies. Another refinement that goes a long way is that all of the game’s 84 songs are original masters by the original artists. No more “as made famous by” covers.

Beyond the core “game,” “Rock Band 2” includes a fairly robust drum trainer application, which acts as a practice module for folks interested in either becoming the greatest “Rock Band” drummer or picking up a real-life kit some day. When you start “beat trainer,” one of three modes, you’ll have 70-some different beats to cycle through in your quest to play the drums. You can slow down or speed up the rate at which the notes scroll. For me, the whole experience brought back memories of having to practice my euphonium in ninth grade, or play scales on the piano when I was 10. It felt more like work than fun, but it’s cool to see Harmonix putting effort into converting some of those fake rockers into real ones.

The decision of whether to pick up “Rock Band 2,” “Guitar Hero: World Tour” or both will probably come down to which song list you like. But with all but three of the songs from “Rock Band” playable in the sequel, plus a robust library of downloadable tracks that includes everything from Mission of Burma to The Who and Queens of the Stone Age, it’s clear that “Guitar Hero” has some catching up to do.

For me, the deciding issue is the way the two games handle failure. “In Rock Band 2,” as in the first game, a band member who fails a song won’t cause the whole band to flunk out of the song immediately. Rather, the band’s score slowly drops in value, providing enough time for bandmates still playing the song to activate Overdrive and bring back the fallen member.

“Guitar Hero: World Tour,” however, is much less forgiving. If one band member fails, you’re done. As someone who likes to invite a handful of friends over, many of them nongamers, for an evening of “Rock Band,” this punitive approach just isn’t an option. People who don’t play games on a regular basis can already feel intimidated when trying to wield a plastic controller. They don’t need a roomful of people giving them icy glares because they just couldn’t figure out the bass part on Sonic Youth’s “Teenage Riot.” Obviously, if you primarily play music-based games with friends who all own these games, you might appreciate the added challenge the “Guitar Hero” franchise will give you. But otherwise, “Rock Band” is the more party-friendly title.

“Guitar Hero: World Tour” is, by all accounts, a great first step in the genre. (In the interest of disclosure, I haven’t played “World Tour,” having decided against building two separate libraries of incompatible downloadable songs.) If you’re coming at the full-band music game genre totally cold and are taking the long view, you’ll have a tough choice to make between the two franchises. But if you’re a current “Rock Band” owner looking for more of the same great party moments the first game gave you, “Rock Band 2” is your game.