Since you own an IM and have had a Metallica in the past, you've played the GOTG playfield before. A lot. It's a solid game, but just about as vanilla as they come both in layout and ruleset. There just isn't anything special about it that you haven't seen before over and over. In an 8 pin collection, I'd have a hard time having both IM and GOTG at the same time, and IM blows it away in every way (other than pure depth...or at least number of modes). If you do go GOTG, save yourself some money and look at the pro. The prem/LE adds nothing of substance, and not much worthwhile as gimmicks either.
BK is definitely more unique all around. It's brutal, but looking at your collection, you seem to like that, LOL. I personally prefer the pro, but both versions have their charm. While it's definitely a typical fan layout, there isn't anything else quite like it with the three knight shots in the middle, especially the flail which is an awesome mech. It has tons of personality and atmosphere, which I value in a game. GOTG is missing that. The Cleland GOTG mod code helps that by capturing more of the movie character, but it is still literally just playing scenes in the background while you play without sucking you in to feel like you are really a part of what is happening. BK feels like you are actually battling these unique characters, and if it doesn't get your adrenaline pumping, you might be dead.
BK's mini-wizard modes are awesome, nostalgic throwbacks to each of its predecessor games. GOTG's mini-wizard mode is a completely unthemed mode that just plays a song that happens to be in the movie. Just zero effort whatsoever put into that one. They could have at least had the Milano flying around the screen or something, but nope...let's just put some cherries up there since the song is named Cherry Bomb...brilliant! Why bother with pesky theming? That's kind of an analogy for the entire game, unfortunately. I loved mine for a few weeks, then once the honeymoon effect wore off I realized there is just nothing special about the game. Solid all around, sure, but not a keeper for me. BK on the other hand, while not one of my very favorite games, is a pure battle with a serious "thank you Steve, may I have another" vibe going on. You will hate it, but love it at the same time...just like your TWD and IM.