There was nothing wrong with Phoenix. When it was first released during my highschool career, my friends and I would spend hours after school trying to one-up each other's high scores. Between us were many countless game-overs with a kill count that probably has a few too many zeros behind it. The gameplay was very hard, but balanced. The graphics(on white background) were clean and precise. The upgrades were fun, and felt worthy to be worked for. In short this game was a 10/10.
Altered Phoenix on the other hand takes all of that and breaks it. The graphics were in no need of an overhaul. The gameplay felt the same, but the balance was lost. Easy gives you too much money for it's own good, but anything else didn't give you squat. Then there's the most important break. The beloved weapon upgrades didn't even work! I bought the L2 weapon, the L3 weapon... Nothing. In short, there is no advancement of firepower. That in itself kills the replay value.
Now for the breakdown:
Graphics: 5/10 They didn't need fixing, but they weren't horrible.
Creativity: 1/10 There wasn't much changed, and what was didn't really work.
Concept: 1/10 Take a classic and break it. Nice.
Controls: 10/10 This wasn't changed. This 10, though, really belongs to Phoenix.
Replay: 1/10 Don't do it!
Overall: 3.6/10.0 Pass it up.