Simply put, Code Veronica is the best in the series.  After RE2 I didn't think the series could get any better but I was wrong.  CV had an amazing graphics and a superb camera system.  The story was HUGE and awesome so this was the most time consuming RE at the time.  I think the remake of RE on the Gamecube is longer (and 10 times scarier than the PSX version).  If you have a Gamecube or DC and love adventure/action/horror games than Code Veronica and the rest of the series is definately for you.