I dunno if I would consider the GBL one of the better indy leagues...they've done well at generating publicity with the Canseco signing and some other stuff, but I really haven't seen anything to indicate that the level of play is at the level of the longer-running established indies or even above them.
From reputation, I'd say the Atlantic League and the Northern League are likely to have the best level of play among the indies, and I'd throw in the Can-Am League as well, given how its teams used to dominate the Northern League teams when the Can-Am was a division of the NoL earlier this decade. Currently, the AtL and the NoL are also known for pushing for better stadium facilities to use than the other leagues do, so that might also put them a step up on the indy landscape.
Of the other 4 indy leagues, I guess only the Frontier League intentionally considers itself a step down from the others, given that it uses much lower minimum salaries and salary caps. Their level of play has reportedly improved though...back in the 1990s the FL apparently looked like a pure rookie league, but nowadays they're apparently slightly below the NoL going by comments I've read by people who have visited games at both leagues.
The American Association is a break-away from the NoL of course, so their level of play might be roughly similar. Well, for the North Division at least...I'm not sure what the Texas/Louisiana-based South Division looks like. That South Division is presumably around the same level as the new United League, given that they were both born from the remnants of the old Central Baseball League.
FWIW, in my own indy universe I'm rating the AtL as AAA, the NoL/Can-Am/AmerAssoc as Double A, and FL/GBL/ULB as Single A. For the GBL and ULB that's mostly based on their status as fairly new leagues (not to mention that they only have 6 teams each), not any hard facts. The American Association is new as well, of course, but the league does include the arguably most well-known indy franchise (the St. Paul Saints) and is run by some of the same people who had been active in the Northern League for over a decade, so I've set the league at the middle rung despite being new. One could probably also argue that the AtL should be set at the same level (i.e. Double-A) as the middle three leagues...I've set it up as Triple-A mostly because my indy-based universe excludes organized ball, so I wouldn't be having an elite league otherwise.
Maybe putting all seven at the same level is the smartest thing to do, heh.
