I got the same feeling playing TNA for the first time. Fun but I does feel a bit empty compared to most new games with ramps, toys, and lots of modes. I would wait before buying one, though. Get some more plays and see if the fun factor holds up. Sounds like Spooky is going to suspend production anyways to get their new game out the door. Prices will probably stay a bit high until more can get out the door. Might as well wait for the market to settle and find a good deal on a used game.

ST pro is a great game for the money. Eskaybee reviewed it well. I love the Vengeance modes but they are not really integrated well with the game. Most people avoid playing them because the risk outweighs the reward. Pretty cool how the magnet instantly fires the ball back at you but dangerous. Core gameplay is really playing out the 18 modes. If they were easier to start and quicker to finish, it would be so much better. I ended up selling my pro because it just got to feel like a lot of work to get anywhere in the game. That warp shot never got old, though.

IM always feels fun when I play it but I don't really know the rules yet. It just seems like there is constant action, excitement, and not difficult to get things going. Sounds like IM fits what you are looking for right now.