Cyber Core - Didn't look great in screens and was constantly compared to cruddy Dragon Spirit, but ended up being one of the busiest little Turbo shooters.
Salamander - Wasn't excited about this because Gradius II let me down, but ended up blown away by its ultra-smooth gameplay and rocking music.
China Warrior - Avoided it for years, but ultimately found it to have a certain pick-up-and-play appeal.
Efera & Jiliora - Looked okay beforehand, but I found myself captivated by its dark theme and great soundtrack.
Batman - Always thought it had potential, but negative reports tempered my enthusiasm. Really cool game that lived up to my original hopes.
Ditto, Dittoed on a bunch of these:
Batman was a revelation for me when folks here and at magicengine were raving about it. First I fell in love with the music, though (listening to mp3's)... only later did I start to actually play it (unfortunately, only through emulation, I still don't own this bad boy).
Guts and Nemo got me into
Efera & Jiliora -- It always looked intriguing, but I read something by them (it may very well have been negative) and I decided to take the plunge. I really loved the aesthetics, mood, and I did not find the game mechanics to be too bothersome.
Salamander: Well, I'm a Gradius fan, but I found myself going back to replay Salamander every chance I got. I can see why it appeals to you: it really improves on the deficits you find in Gradius (sluggish ship, power-up system, pacing, etc.).
CyberCore, which I bought from Electronics Boutique back in the day because they reduced the price to $30, was somewhat of an impulse buy. I loved shooters, but I was really worried that this would be another Deep Blue. No, I had not read any reviews. I was going in blind.
China Warrior, of course, I appreciated since the TG-16 launch. I'm glad you have found that it has "a certain pick-up-and-play appeal" -- I've likened it to a "rhythm game" where you achieve a Zen-like state of twitch-response to the things thrown at you and you just keep smacking everything out of your way. Sure, some folks can memorize the stages (and it is important to remember particularly tricky sequences), but overall, I don't rely on memorization. Just good old twitch-reflexes can get you through a lot of it. I love that. But you have to achieve that Zen-like state, otherwise you might feel like you are constantly trying to "catch up" to the pace of the game.
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Pleasant Surprises
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Gomola Speed - Initially, this game looks (and feels) like it won't cut it. But, very quickly, you realize how friggin' sweet, how addictive, and just how grand this game is. The only downer: I've come close to getting blisters on my left thumb from the direction pad (those moments when I'm desperately trying to survive!). I always include this game in the "Underappreciated" threads.
Timeball / Blodia - I avoided this back in the day. Yes, I did. I didn't want to pay good money for this game. When it was reduced to $20, I picked it up along with TRICKY KICK! Timeball has a lot to be desired (the visuals should have been more polished, I like the songs, but they should have included more tracks, etc.) -- but only in the superficial sense. The meat of the game (the game mechanics, the puzzles, the challenge ramping up) are great. I think most people aren't even aware of the "turbo" button that speeds up the ball.
Tricky Kick - This game is really, really addictive (in a weird way). I guess I like puzzle-action games, in general, and this game, despite all the problems (the sprites are friggin' microscopic, try playing this on a TurboExpress!) ....well, despite everything, I kept coming back and trying to get to the next level / stage. I found myself saying, "Why do I want to TrickyKick again?" Then I'd respond, "By all rights, I should be sick of this game, but I want to try to beat the stage just one more time."
I'm too lazy to write more stuff...