Well I would expect a 20 since I've never seen a Fighter without STR 20. And I'd expect an expertise type feat for another +1. So +10 before stances/powers.
The two 4e 1st level PCs I've made recently were a Dragonborn Warlord who had DEX 10 & +8
to hit (STR 20 +5, +1 feat, +2 prof), and a human Slayer who had max +11 (Str 20 +5, +1 feat, +1 weapon talent, +3 prof, +1 stance). Over the years I've not seen much evidence of PCs starting with 18s - I guess there was a half elf Ranger in 2011 started with 18 DEX.
You'll not too often see a +7 level 1 fighter, but its a reasonable build (+2 for axe, +4 STR, +1 FWT).
That 2nd build is why the 1st build ends up existing...or the closer variation, the Dwarf with Dwarven Training and a 16 Str.
From an optimization standpoint, they're both a little off - one person is following an optimization rule without questioning it(invest in to-hit is a good thing!) and the other potentially isn't following that rule at all. At worst, the 1st is going to be over-invested in to-hit. Nothing too wrong with that. But the 2nd might not be investing in to-hit to make up for the (relatively poor) starting value.
But everyone's seen enough of build #2 to realize that having a +2 proficiency or 16 starting Str often means bad or even really awful at hitting. And instead of going, "Hey, maybe that player doesn't know what they're doing?", they go, "Wow, that build that player is using an axe and keeps missing all the time. Having an axe sucks!"
The real rule is to be able to get where you want to go as fast as you can and then land as many attacks as you can. This means going first. This means having a high to-hit. And it means getting as many to-hit rolls as you can.
As a Fighter, Rain of Blows is an easy way to get 3 attacks. MC'ing Monk for Eternal Tide lets you attack a target and pull another one next to you - who is now slowed and can't shift. Power swapping for Quicksilver Motion lets you free action move at the start of combat. As an Elf, you could free action move, move again, charge for 21 squares of movement, AP for Rain of Blows and the target now can't shift away from you and is marked.
Say that was the BBEG Artillery with a big area attack? 3 main options:
He doesn't do the big attack - attacks you instead
He does do the big attack and provokes an OA and Combat Challenge(for violating the mark)
He tries to move away(OA) which can be stopped by Combat Superiority and has a bonus to hit from Wis, then Combat Challenge again on a hit as he tries to target the group.
See any combats where that might be useful in the context that the Elf starts with an 18 Dex and therefore has +4 Initiative over the 20 Str build? 21 squares is a lot of movement to still have a minor action left...