Long before eating bugs and diving from rooftops became common weekly TV rituals, MTV ruled reality with a breakthrough series that followed the lives of young adults living together for the first time.
  As recently as last season, “The Real World” was still doing fairly well. But now the formerly addictive cable show that started it all may be fizzling into obscurity, buried buzz-wise by the very MTV shows that it begot: “Punk’d,” “Newlyweds” and even “Viva La Bam.”
  “Real World XIII” finished its season amid little fanfare last week in an increasingly competitive cable time slot.
  The “Real World” finale was still tops for the night, but the show finished third among adults 18-34 and seventh among adults 18-49 for the week, down from last season’s No. 1 and No. 2 finish in the demos.
  It was also off by 31 percent among its target audience of 12-34s compared to last season’s finale, averaging just a 2.9 rating.
  In addition to 13 seasons of the over-dramatized “Real World,” MTV has introduced America to “Road Rules,” “Real World/Road Rules Challenge” and a slew of celebrity-based reality shows like “Punk’d,” “Newlyweds,” “The Osbournes,” and “Rich Girls.”
  Some of those shows are now gaining their forbearer. The season finale of “Newlyweds: Nick and Jessica” in October had a higher 12-34 rating than “Real World’s.” Among 12-34s last week “Punk’d” was just 21 percent behind “Real World.”
   Besides an onslaught of salacious reality programs across a number of networks that make Puck look tame by comparison, “Real World’s” Tuesday 10 p.m. time slot has seen stiff competition this year in the form of two buzzworthy new shows, FX’s “Nip/Tuck” and Bravo’s “Queer Eye for the Straight Guy.”
   While “Nip/Tuck” is done until next year, “Queer Eye” nipped at MTV’s heels as the second-highest rated show last Tuesday among adults 18-34 behind the “Real World” finale.
   In other cable ratings news, MTV’s sister network VH1 celebrated a ratings coup for the weekend’s broadcast of “VH1 Big in ’03,” with a 1.3 rating in adults 18-49, more than double last year’s 0.6 rating.
   HGTV’s holiday specials on Friday after Thanksgiving earned the network a 1.6 household rating, making it the network’s highest-rated primetime night ever.