Definetly FE9. Generally, the later FEs were.are better than the old ones.
FE9 is the best FE ever, imo. Because all FEs have the same gameplay... it's differentiated by its story, which is the best in the series.

Most all Fire Emblems have about the same general story (big country invades little countries, hero/lord fights big country).

The big differentiating factor for me is the cast and I think Fire Emblem 7 has the most likeable cast.

I've been playing FE:PoR while I banned. I'm at Ch. 27 and several of level 20/20 units suck. I'm too far to restart now though.

FE10 is the best for me. It's the longest, has some great characters, and has tons of characters (a huge plus). It also has the best music, and is one of the hardest.

FE9 is pretty good (playing it right now). It has a fairly dull start, and an obvious story. You see where you're going every time. Music isn't that good

FE8 has a good backstory, but the core plot is pretty dull. The maps and enemies aren't as interesting either. Great music

FE7 has great characters, is one of the longest, the best backstory (which is really what matter. The core plot isn't that special, but the backstories rule). Good music, but not as great as the best ones.

FE6 lacks a lot, but it has a more interesting map setup than most of the others.

Note: How I feel about this changes depending on which game I played last. Still, FE9 and 8 will always be considered inferior to FE10 and 7.

I like FE8's cast more than FE10.  A good portion of it is that I simply don't like Ike that much as a lord.  Pretty much all the FE7 lords crush him in terms of personality and even FE8/6's lords are on par or better than Ike.

FE6 would be better if it were made today though.  A lot of the stuff that's missing is the extra fun stuff like special boss conversations with certain units, banter between missions, etc.  During the GBA era, they were experimenting with perspectives.  FE6 had a narator.  FE7 had a tactician.  FE8 was a story perspective.  FE8's perspective worked the best IMO and it's the one used in Radiant Dawn.

The more you look at the series, the more you begin to notice just how much it has grown and matured over time.

The actual amount of change during the GBA era alone was amazing. 

I can't wait for the next full installment of FE, every new version (except 9 to 10), has several changes that keeps the games very distinct amongst themselves.

I'd say FE10's skillswapping, fixed BEXP, and biorhythm were plenty to make it "distinct."

Quick question, I just finished ch. 27 of PoR and I didn't defeat the Black Knight........ long story short, Ike would have died.

Does that alter to plot dramatically?

Another question.. I have a boatload of Bonus Experience I've never used and several low level units I seldom use..

Should I use it on them? I'm interested in getting at least 20/10 for Rolf, Mist, Jill, and Tormod

1) The Black Knight doesn't come back if that's what you mean.

2) There is really no reason not to use it at the end. Ending the game with a ton of it won't really help you.