Nah, The Last Blade has a completely different style of gameplay than Samurai Shodown, not to mention a completely different setting. They're both great; if they had made a SS game with the LB engine, all the hardcore Shodown fans would have been completely pissed off. LB is much more combo-oriented.
Actually, though, you could almost consider SS 1-2 (& maybe 5) and 3-4 to be different series as well. After playing SS2 for a while it is very difficult to play 4, and vice versa.
I'll vote for the FF series as well, though; also, I agree MOTW is great, but everybody should play the Real Bout games (particularly Special and RB2), since they are incredible as well. And, of course, Fatal Fury Special is an all-time classic. I have a lot of love for SF2CE, but FFS just blows it out of the water on so many levels.