Well, it depends on how devout a fan you are. Casual fans that already have the game in some form may want to hold off till this goes on sale, if only because it just leaves a few extras that, while cool, don’t entirely justify the $40 price tag.
Now, if you’re a fan of the series or want a proper introduction, then, yes, I’d say that Sonic Origins is worth the cash. The beautifully animated menus are a thing of beauty, the new animated sequences are a lot of fun, the extras are abundant (unless you just get the standard edition, which is okay), and the four included games aren’t bad at all.
Would I like to have seen more games? Sure. Sonic Jam would’ve made a good historic piece for the collection; Sonic R is an underappreciated racer that deserves a full-blown re-release; and even Sonic 3D Blast had its moments, even if it wasn’t everyone’s, ahem, speed.