When Speed came out and was VERY successful, it was considered to be a "sleeper hit", because NO ONE had high expectations for it. It hadn't really been hyped up or anticipated by audiences and critics. It's like it just suddenly showed up one day and knocked everyone's socks off. Keanu Reeves was still considered to be a joke to a lot of people at the time, even after hits like Point Break. So when Speed came out and turned out to be a really, really good action thriller, critics and audiences were kind of taken by surprise.