My first regular gaming experience came with the C-64, with Sanxion and Delta and some other lesser shmups, but the first to really catch me was
Armalyte

Released 1988 by Thalamus Ltd.
A quite standard hori shmup, in fact, but it had its good points. By some reason or another it got a terrible review here on shmups.com, but personally I have never met any C64-gamer who didn't like Armalyte.
I remember that the charm points I fell for was the fire power of the ship (quite big to be a C64 game) and the big amounts of enemies (more than the hardware theoretically could cope with). I also liked the instant respawn system, which was rare at the time (did it even exist in other games?) and also the fact that you didn't lose your power ups when you died (also very rare at this time, although it was actually the fact in Delta). Ever since I've disliked shmups where you lose your power-ups upon death (the only thing that saves Gradius V is that you can pick up your options), since this normally means you practically have only 1 life.
I also liked the level designs. Quite opposite from the review on shmups.com, I felt each level had it's mood and style, and you sort of got to know each level quite thouroughly. Some tech, some crystals, some giger... for the C64, it didn't get that much better. The review referred to the colourful graphics. Maybe on an emulator. On a standard TV with composite video or antenna input (which was the fact for 99,999% of all C64 players), it looked great.
The game allowed two player simultaneously, which was great. If playing alone, you had a sort of option (extra ship) that also acted as a shield. Sometimes it felt like cheating, so I always preferred the 2playermode if possible.

The weapon upgrade system was sort of standard: On each stage there appeared some wort of crystals that when shot on changed form to different power-ups, and when picked up had the effect on the ship. The amount of fire power was vastly larger than for most C64 shmups. The ship started with firepower 2 forward (meaning maximum 2 forward shots on screen at any given moment) , but could be upgraded to 4. A tail gun and side shots were avaolable, as well as a "trident" that broadened the front shot.
There was a so called "super weapon", fired by holding down the fire button. There were three types: The thick laser that could shoot through the background, a wide spreadshot that fired both forwards and backwards (the closest you could come to a smart bomb) and a pulse laser. The pulse laser used to be the best, since it could easily be used to change the crystals in quick seccession to the high power power-ups.
The super weapon used up energy from a battery. Each ship was equipped with 1 battery, but this could be upgraded to 5. You could also pick up generators to make the batteries charge faster.

One peculiar thing that I still think was a great idea was that after each level, the ships lost all its fire power. But you did keep half of the batteries and generators you'd picked up, though.
In retrospect, this was actually quite a good idea,that I would very much like to see in a shmup today. There was no "this level is so difficult if you haven't this or that extra weapon when you enter it", every level was a fair challenge for anyone, no matter how badly or well you'd done on the previous level.
The difficulty level was good (for me). Unlike many other shmups from that time it was just averagely difficult, not hear-tearing difficult like Sanxion or Io. I replayed it again a while ago, and it was still level 5 (out of 8) that got me; the same that I was stuck on forever when I was 15.
To the bad parts... Just like the review on shmups.com states, the bosses are really tedious. But the fact is, I never paid them any attention. They were just the point in the exclamation mark, so to say. A decoration. They moved a bit, shot some weeny bullet and then restarted. Not much. Normally, you didn't die on the bosses, they were just there to mark the end of the level. For me, I didn't care. I didn't know bosses were supposed to do something more, so I wasn't disappointed euither. It didnt matter. The levels were enough.
The worst defect was that the explosions had the same colour as the ships they came from. This was a hardware thing: It was impossible to have it otherwise. Worse than that was that the explosions kept moving in exactly the same fashion the ships would have. Was quite unnerving. Also, being able to pass through the solid background just because the ship had an invulnerability shield felt really tacky. But well, hardware, hardware.

Today Armalyte is probably no more than nostalgia for the C64 gamers. Still, I still like it, and now and then I dig it up to have a go. To clear it again (no continues) is a modest goal. All that counts it to remember enemy formations. No bullet patterns here.