Celtics
Starters:
C - Perkins
PF - Garnett
Bench:
PF / C - Rasheed
PF / C - BBD (most likely)
PF - Shelden Williams
PF - Scalabrine
Lakers
Starters:
C - Bynum
PF - Gasol
Bench:
SF / PF - Odom
SF / PF - Walton
PF / C - Powell
PF / C - Mbenga
Odom probably makes more of an impact than Rasheed, but not necessarily. Gasol versus Garnett is close-ish but if Garnett is healthy he's significantly better. Perkins and Bynum is tough to call simply because Bynum does have more talent but Perkins is far more consistent and much less likely to have a season ending injury. Once you go beyond the first 3 guys, the Celtics clearly have an edge. Walton is a solid role player, but as a PF he doesn't really compare well to BBD, and Powell and Mbenga don't really have anything on Williams and Scal.
You could also say that Artest counts, because he can play PF if necessary, but as that would take minutes away from Odom or one of the starters, I think it's a wash. Artest is not better than Odom.
So perhaps you could argue it one way or another, but to say that the Lakers clearly have the best frontline is preposterous. It's not clear at all. In fact, I'd venture to say that the only clear disadvantage you could say the Celtics have is that the Lakers overall have more height, but it's not really a big enough advantage to matter (just an inch or two here and there).