Usually it depends on the strip in question. It's not a bad thing, no no no, but it's sometimes easy to point out (especially if you're one of those serious writers....)
Two-dimensional/One-Dimensional comic strips usually include funny ones like: Garfield (That's the major one), Peanuts (some of the cast), Marmaduke, B.C. (sometimes)
Three Dimensional ones include ones like those of Peanuts (some of the cast), Marmaduke, Family Circus, some of the classic Disney Comic strips, Blondie, Calvin and Hobbes, Beetle Bailey, Hagar the Horrible, Astrix and Obelix, B.C. (sometimes), Dick Tracy.
All of which are wonderful newspaper comics I can think of, but each with their own moments of two-dimensional and three-dimensional characters. 