SANTA MONICA, Calif., Feb. 20, 2000 -- Didn't get enough of Ben Affleck in "Boiler Room"? Well, not to worry, for said heartthrob actor pretty much achieves multiplex ubiquity this Friday with the much-delayed bowing of "Reindeer Games." In the John Frankenheimer-directed flick, Affleck plays an ex-con, fresh out of the slammer, who's coerced by his ex-cellmate (Gary Sinise) to pull one last heist on the night before Christmas -- which explains the scene in the trailer where a bunch of Santa Clauseses are walking in, or out, of, well, somewhere. But what the Xmas angle doesn't explain is why the studio (Miramax's Dimension Films in this case) kicked the film's original release date of December 1999 all the way back to mid-February. (Saving the best for last? Or, well, mid-winter?) Here's a look at the other films opening this week: -- Going up against Affleck and