Ok then if we are talking an all fighter situation, with everyone using only normal equipment (being a test of skill rather than wealth) then perhaps 8 or so 1st level fighters should be a good match for a 10th.
I do think being outnumbered should matter far more than it does in D&D.
I don't like this question because level 1 characters aren't going to be fighting level 10 characters (at least, not in my game). How many goblins a level 1 character can take on, versus how many goblins a level 10 character can take on would be a more helpful way to look at levels. Even then, the answer would largely depend on how they define level 1, whether it is more of an apprenticeship level or a heroic level, and it would also depend on class design, resource structure, etc.
What? Goblins can't be characters now? You goblin-racist. I bet you're one of those Kobold-lovers, aren't you? The answer to "how many goblins can an Xth level character take on?" should always be "depends on what level the goblins are".

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.