I've covered other Super Robot Wars games, and while they have some original content, they always involve crossovers of content licensed from other sources. One day, Bandai Namco figured "why not save money and cut licensing costs by using all of our own strictly in-house material for a mecha turn-based strategy game?" Hence, the "Original Generation" series was born.
The first game uses the original portions of the following games, in whole or in part:
Super Robot Wars Gaiden: Masō Kishin – The Lord Of Elemental
Super Robot Wars 2
Super Robot Wars 3
Super Robot Wars F
Super Robot Wars F Final
Super Robot Spirits
Super Robot Wars Alpha
Super Robot Wars Alpha Gaiden
Super Robot Wars IMPACT
Super Hero Sakusen
Hero Senki: Project Olympus
The plot is split into two halves. The first half depicts the Divine Crusader rebellion, in which the scientist who warns the complacent people of Earth to be ready for invasion launches his own invasion against humanity to get them to take the threat of imminent alien invasion seriously. The second half is when the alien threat called the "Aerogaters" finally begin their invasion, and your heroes must combine their forces to defend humanity against them.
There are two routes you can pick at the start; one playing as Ryusei Date of the SRX Team, and one playing as Kyosuke Nambu of the rival ATX Team. Both routes are canon up until the two teams join up, after which each has a unique concluding route--though the second game establishes the Ryusei ending as canon. Regardless, both offer specific challenges and differences that make them worth playing.
The gameplay is that of a turn-based strategy RPG set on a grid-based map, with visual novel-style cutscenes for story and intermission scenes where characters and pilotable mechs can be upgraded. Unlike the games with licensed properties, the "Original Generation" games allow switching out almost anyone into most other units and much greater unit and weapon loadout customization. Part of the meta-game is to determine the best setup for your needs, though some stages require certain machines and pilots for story reasons.
Graphically, this is an early GBA title (though translated to English much later) and it shows. While the team made good use of colorful graphics and visual novel-style scenes to tell a good story, the animation is very limited in battle scenes. They do try to make up for this as much as possible, but the animation is still pretty poor and stiff looking even at the best of times. The characters and machines all utilize a very hand-drawn anime aesthetic to match the series penchant for drawing from licensed anime properties that fit the theme like a glove.
Music and sounds make good if not outstanding use of the GBA hardware, providing excellent chiptune-style music that tends to be very synth-rock in tone, and feels right out of a dramatic mecha anime. Sound effects for impacts, gunshots, melee attacks, and other things redeem some of the stiff animations to a degree, sounding very pleasing to the ear. Controls are mapped to the D-Pad and the basic GBA buttons and are not difficult to learn, with several easy early stages to ease you into the controls and teach you some of the more advanced concepts.
Game stability is excellent, with no issues loading it on a GBA or a Nintendo DS. The English translation is a mid-2000 Atlus effort, meaning it is fairly competent, with a few minor name screwups and a bugged battle line or two (mostly where they extend past the text box). Overall, all the essentials are intact in regards to accuracy to the source, with only a few minor liberties at best taken to localize some concepts better for non-Japanese audiences.
Morally, this is a game depicting war, so it's got some issues. Violence is of the RPG style, where you give orders and watch them happen. Your team is happy to accept stand-downs and surrenders, only fighting back when that is not an option the other side will take. While no blood or gore is depicted, characters are mentioned as dying, but in-game all "dead" machines and their pilots immediately disappear after their destruction.
Language is about the mild PG-13 level, with most PG related swears and a few b***rds and an occasional s*** at rare intervals. Some dialogue is a bit crude, with some double entendres, though some are far more innocent in context. Sexual content is pretty low, with only a brief mention of a visit to a beach without any description of more than just bathing suits at worst.
It is very uncertain when one female character got pregnant (hints that this happen are implied towards the end of the game), but whether they were married at the time or were married after is not made clear. The parties in question are confirmed married and the woman in question is several months along by the sequel, so whether this was before or after the final battle (and being married) is unknown.
Telepathy and psychic powers do exist in-universe but are regarded firmly in the context of science and play a plot role in several machines augmented with such abilities. Some enemy forces crib from the Jewish and Christian Bibles for names of their machines and characters, like mecha named after biblical prophets as their production codenames. No specific religious meaning is ever implied from this, nor is any deliberate blasphemy intended.
One character has two talking cats referred to as "familiars", but it's made clear they are not the occult version (though it's brought up as a frame of reference for the concept), more they are aspects of the consciousness of the pilot of the machine their owner uses so they can help operate its equipment. Given the fact they exist due to manipulation of thought (similar to the hard science telekinetic powers mentioned prior, albeit their existence defies easy classification), they are based on some technology that is not fully explained in-universe, though even characters in-universe are at a loss for how.
There is one character who appears to have a form of extrasensory premonition, being able to sense people from far off distances. While left vague as to whether it's of supernatural origin or based on known science in-universe, in-game discussion of said ability and game lore heavily indicates it's merely another form of the known scientifically based ESP abilities that is a game element and plot point. The issue is never definitively cleared up one way or another.
Morally and ethically, your forces observe the rules and customs of war without fail. Some mention of child soldiers and depictions of brainwashing by the villains are shown, though condemned as atrocities. Any acts of war crimes like poison gas or reprisals against innocents are also condemned in the plot and your team takes pains to not only avoid such things, some missions are dedicated to preventing such evils. Not all the superiors of your characters are completely forthright or honorable, but all lawful orders are regarded as worthy of being obeyed and strict military discipline is encouraged to be respected.
The first Original Generation is a bit rough around the edges, but given the fact it's one of the very few Super Robot Wars games in officially translated English (released in North American territories without the need for import) and remains very fun despite its flaws, I recommend it highly. Morally, it tells a story that any teenager or older should be able to handle maturely.