Unless you wonder how characters from Street Fighter 2 compare when fighting characters from newer games, don't bother.
Let's begin with the positive...The graphics are sharp, but this expected with a 2D fighting game from Capcom. Controls are responsive and balanced. Sound is on par with games like Street Fighter 3 except with a totally uninspired sound track. The good things stop here.
And let the bashing begin... The game's worst feature is it's purity. Weird to say but it's true. The game doesn't provide anything to try to balance the game. Characters from Darkstalkers have about twice the speed of Street Fighter 2 characters since all fighters keep the attributes from their games of origin. Another example of this is that characters from Street Fighter Alpha have their trademark Super-Combo bars which charge up more than one level. Characters from Street Fighter 2 are stuck with their one-bar one-move limit. Character from Street Fighter 2 can only block while the characters from Street Fighter 3 can block and use parrying. This balance thing even goes into the controls as well. Moves in Darkstalkers are way easier to perform than say, Super moves from Street Fighter 3. The selection of characters leaves a bit to be desired too. The fact that you have to pick two characters for your fight is cool but being able to swap them on the fly would have been nicer (you can only switch between rounds).
All in all, this game is not worth any amount of money unless you and your friends have an ongoing argument on who would win between Ryu from Street Fighter 2 and Demitri from Darkstalkers.