Ask most Mac users for agreement on what computer game they really play most often, and the answer most likely won't be Quake II or Riven but that lowly time waster that came bundled with their machines: Eric's Ultimate Solitaire. So who's Eric? He's Eric Snider, 29, a software engineer for the California-based software company Delta Tao. Snider first started riffing on old solitaire standards like Eight-Off and Klondike while an intern at Apple in '91, and the sampler game was first packaged with Macs in '93, with a PC version becoming available in December '97. Unfortunately, Eric's Ultimate has put his company on the map but not in the money. ''I've heard that some people think I'm some kind of millionaire because of the sample,'' says Snider. ''Apple didn't pay [the company] for the sample. I make money when people buy the full version.''