The Ultimate Marvel series are revamped versions of the classic characters. It's not necessarily Elseworlds, but just a revamped version, kind of like comparing pre and post Crisis DC characters.
Instead of beginning in the 1960s, all the Ultimate characters have started in the recent years. Spider-Man is much younger, the Ultimates (their version of the Avengers) has just formed, Daredevil has just become Daredevil, etc. Because of the Spider-Man and X-Men films, Marvel considered relaunching their titles to attract new readers and to clear up all the years of continuity and confusion (kind of like Crisis). Word leaked out, Marvel decided they wouldn't and denied ever thinking it, and Marvel keeps the Ultimate verse seperate.