It sounds as if you are trying to decide on a camera purchase.
As Bernie observes, here is no one "best" camera. We all need
different strengths in our cameras.
As a good example, try answering yourself : "what is the best car ?"
If you would care to say what your needs are in a camera, there are
some very expert people hanging out here ( not me

who could point
you in the right direction.
Back to your original question ( thank goodness, a non-S5 comment
Re the S2 and S3, it really boils down to money. The S2 is a wonderful
camera and was an absolute revolution for Fuji when it came out in 2002,
BUT, it is dated. If you found a good used one, it would still be "used"
and liable to potential problems.
I love my S2, but the S3 has enough "tweaks" and upgrades to its
performance that it is indeed a "better" camera, if you are comparing
just the two of them.
If you wait for a few weeks or a couple of months and really want to save
cash outlay, there will be many S2 users who will upgrade to the S5.
They will be selling their S2s at bargain prices.
Knowing what I know now in comparing the S2 and S3, I would say
that the S3 is worth the extra money. S3 prices right now are between
$1000 and $1300 in the USA.
Keith
--
Not a word was spoken, the church bells all were broken . . .