Well as you remember, Miami did lose a home game but won the series anyway. The Spurs are in decline, their big three are on the downside of career while Labron is at his peak.
Besides missing the Game 3 prediction, I think you have it fairly wrong. James is at his peak, true. Duncan has played better the past 2 years than the few years before that (but was still a very solid/good player even then). Parker is in the late of his prime and Ginobili is one of the best 6th men out there.
Wade is on the decline and Bosh never played to the level of the others outside Ginobili maybe.
The biggest difference here is the team. The Spurs are solid and deep - they win playing as a team. Take away a piece of Miami, and they fall apart (especially if that’s Lebron, although I don’t think he could have won Game 1, only lessened the blow). The Heat don’t have anyone like Kawhi Leonard - young, strong, great shooter, great D. They don’t have a capable big man to take on Tiago Splitter or Aron Baynes (if it comes down to it, although not particularly strong players themselves). Danny Green and Ray Allen match up pretty well, but I’d give the edge to Green due to youth and better defense. Boris Diaw can play D like Birdman, but also can shoot it - Birdman looks like he doesn’t want to touch the ball unless the other team has it.
Who else is there? Chalmers has been nonexistent in this series - I’d take Patty Mills over him any day. Matt Bonner & Belinelli can play ball especially the 3, but don’t get put in as often as they should (with such a deep team, it’s understandable). What do the Heat have left? Battier? Haslem? I guess I forgot about Rashard Lewis, but still…basically the Heat are 7 players unless fouls warrant it. The Spurs Bench can field a solid team (and nearly beat the full strength Heat earlier this year).
Series isn’t done yet, and I think it’s a good matchup, but to say it so simply is really overlooking the details.