Unless they are bad rips.... NO.
See... DVDs are mostly 720x480 or similar resolutions (widescreen). Rips are either slightly smaller, usually 640 or 672 in width. From your signature I see that you're using 19" monitor, I presume you're on 1440x900 resolution. That's exactly the double width of actual widescreen DVD. Does it look pixelated? No, right? Does any of your current DVD rips look pixelated? Again No, right?
Video scaling in players is quite different affair than Image/photo scaling in image viewers... if your concern about pixelation is based on that experience (ie. when you zoom smaller image on large display, it looks pixelated)
So, you can guess from that... that unless they're bad DVDrips, they shouldn't look noticeably bad.