Yeah I think reason we haven't seen Ishtar on the list is because almost nobody has ever bothered to watch it.
Same goes for Gigli. Nobody has actually seen it, so it doesn't get mentioned.
AFA Gattaca is concerned. I think I'm closer to Hick's opinion. I felt it had a great premise, but completely botched the execution and ended up tending to be boring (I'm not sure I'd go fully boring on this one).
AFA as does "slow pacing = boring". I'd say that almost all boring movies are also slowly paced. Fast pacing conceals a lot of flaws and usually demands you stay attentive, so it's a lot harder to think of any face-paced films that seemed boring.
However, the converse is not true. Just because a film is slow-paced does not make it boring. But it ends up being very subjective. For instance, I love the extended LOTRs. They all could have been another couple of hours long and still wouldn't have been bored. But I can understand how others would find them way too slowly paced and thus boring. My only complaint about LOTR is that the Battle of Helm's deep seemed to go on forever. If they had extended it just a little bit it would have been in "real-time".