Here's the fiefs that you can actually choose as a starting location if you want to play the game without getting immediately run over:
Uesugi (2) : Really strong all around, with a good starting position. I just sat there building up my city for a while and then nearby fiefs starting sending me gold for non-aggression pacts and marriage pacts, which was cool.
Tokugawa (8) : About as strong as Uesugi but has a highly contested starting position. Lots of fighting all around you. It's probably best to let them focus on the weak territories and exhaust their own resources, then try to expand. If you try to expand quickly, you'll be left stretched thin and get attacked from multiple sides.
Kitabata (13) : I didn't test this one myself but it seems like a slightly weaker fief than the above two. Hard, but playable.
Miyoshi (15) : This one is on the average/weak side BUT it has a special property that is worth noting. The merchant is ALWAYS available in this territory which makes it a really interesting choice if you want to go for a more domestic playstyle. As a bonus, the territories around you are fairly weak, so they most likely won't bother attacking you for a while and you can play the simulation game.
Takeda (16) : Just like Kitabata is the hard mode version of Tokugawa, Takeda is like the hard mode version of Miyoshi. He's got about the same strength and also starts out in the non-contested section of the map. Only difference is that you don't have guaranteed access to the merchant, so it'll be a bit more challenging.
Oda (17) : Obviously if you pick Oda you'll have a pretty good path to victory, since he's the strongest starting commander. That being said he actually does start in a highly contested area right in the middle of the map. I would actually go as far as to say that Uesugi is the best starting position if you want an easy game, while Oda is the strongest option to play a 'normal' difficulty game but with a strong character.
I actually went and looked up my list of good territories to start with in Nobunaga's Ambition, just in case anyone wants it. Might as well post it now and have it available, rather than waiting till someone asks and them having to wait for me to find it.
This is for the game mode with the smaller map, not the map of full japan. But this would also be the easiest mode for a new player to get into anyway because the game is smaller and therefore faster to complete.
I beat the game with Uesugi Kenshin, starting in area 2. It allows you to gain a foothold in the right side of the map and slowly work your way from right to left.