In the CBI, the Japanese Army had a major edge in the early years with their aircraft led by the Ki-43, with the less capable Ki-45 twin engined fighter also playing a role, and in the early months the comparative fragility of their bombers like the Ki-21 didn't seem to matter much. We tend to focus a lot on the fighters, for obvious reasons, but as air superiority remained at least contested for most of the war in the CBI, it's important to consider the role of the bombers as well.
The Ki-21 "Sally" was fast (300 mph at 15,000 feet, cruise speed 236 mph, defended by 5 x 7.7mm and 1 x 12.7mm mgs) and had a fantastic range for an early war bomber of 1,680 miles. But as the war shifted away from Blitzkrieg type shock warfare and settled into attrition, that vulnerability particularly for the relatively cumbersome bombers started to tell. The IJN's G4M "Betty", also used in Theater, was a bit more robust but slower, (266 mph, 196 mph cruise speed, 1,700 mile range, 4 x 7.7mm mg and 1 x 20mm cannon) seemed to do more damage in bombing raids and suffer less attrition, as well as being a fairly lethal torpedo bomber particularly against merchant shipping. This edge may have just come down to the better training standard of IJN flight crews compared to the IJA. The IJA also had a very useful recon asset in their excellent and beautifully designed Ki-46 "Dinah" recon plane.
The British potentially had an advantage but they deployed older aircraft types and took a long time to adjust Tactics. We already discussed the limitations of the Hurricane, (though it proved quite capable of shooting down Ki-21s) the other big weakness on the British side (to me) was the Blenheim bomber, which remained one of their most important attack types through the end of 1942. Blenheims (266 mph, 198 mph cruise, a good range of 1,460 miles, defended by 3 or 4 x .303 mgs), though they did have some protection and self-sealing tanks, seemed to be as vulnerable to fighters as the Japanese types. It carried a light bomb load and did not have great bombing accuracy and overall contributed relatively little to the war effort in the CBI while costing the lives of many trained crew and using up valuable resources.
However the British were able to make a major leap forward in (theoretical) capability with the introduction of the Beaufighter and to a lesser extent the Mosquito in Theater in April / May 43 initially in small numbers. The Mosquito proved to be a valuable recon asset, though the wood construction caused some problems in the humid and rainy environment. The Beaufighter in particular had a significant impact. This would have been more telling if more of these planes had been available sooner. Both were accurate bombers and in the ground attack role and had comparatively low loss rates on missions. The Brits also used fighters in the fighter-bomber role with success, as they bombed accurately and could do some real damage strafing, while suffering relatively low attrition (compared to a Blenheim or a Ki-21).
The Japanese did also produce some good new bombers, the Ki-49 Storm Dragon / "Helen" (operational from late 1941) had armor and self sealing tanks, yet still managed 306 mph / cruise 217 mph, with a 1,200 mile range, albeit with small bomb load. The even better Ki-67 Flying Dragon / "Peggy" which didn't become operational until 1944, had armor and self-sealing tanks, could make 334 mph, cruised at 249 mph, had a 1,700 mile range and was armed with 1 x 20mm and 5 x 12.7mm machine guns. It too had a light bomb load but was accurate due to dive bombing capability. The Japanese Navy developed the similarly performing Yokosuka P1Y Ginga "Frances" (arriving in 1944), which had 340 mph at 19k feet, an incredible 3,300 mile range, 1 x 13mm and 1 x 20mm guns and a light bomb load. It was used in the CBI but was severely hampered with engine problems. However none of these bomber ever really found their niche. The Ki 49 though good, was not available in sufficient numbers in time to have a telling effect in the crucial mid-war years, while the Ki-67 and P1Y did not become operational in time. The Ki-67 was roughly comparable to a German Ju-88 but two years too late. The P1Y could have been almost comparable to a Mosquito but was so crippled with design and maintenance problems it's hard to say if it was really as good as it looked on paper... and it too arrived two years too late. Nor did the IJA field a satisfactory replacement fighter in time in the same period to protect them.
The problem with the Ki-49, Ki-67 and P1Y were basically production, especially the engines. This, to me, was the major Strategic advantage the British had over the Japanese: they were able to keep producing good new engines through the war and get them in working order relatively quickly (albeit with some exceptions of course, Napier Sabre comes to mind). Engine production as well as indecisive meddling on the planning / procurement side really hamstrung Japanese aircraft development leading up to the crucial mid-war period, and they famously never did really introduce satisfactory replacements for their early war fighters (the excellent Ki-43 and A6M) and instead only made incremental improvements*. The new bomber types came in very small numbers - Japan only produced ~ 700 Ki-49s through the whole war, while almost 6,000 Beaufighters and roughly 6,000 Mosquitoes were produced by 1945. The British meanwhile had the Spit VIII coming into the theater and the US had the P-38 and P-47 coming available in 1943, and later the P-51, while around the coastline, the Navy Hellcat and Corsair also arriving in 1943, all of the above used as fighter-bombers as well as fighters (something neither Japanese fighters or dive bombers ever really worked out well for against land targets), while early war B-25s and A-20s were kept in the game (albeit not quite as good as a Mosquito or a Beaufighter), when they were modified for strafer and skip bombing Tactics that made them quite dangerous to the enemy and effective as bombers.
I think the British could have better leveraged their advantage in producing excellent engines like the RR Merlin and Bristol Hercules by hurrying the retirement of aircraft like the obsolescent Hurricane and obsolete Blenheim, and producing even more of their excellent and much more effective aircraft like the Beaufghters and Mosquitoes, (and of course Spitfires) if that could have been possible. The production of newer and better engines was the Achilles heel and a major bottleneck for the Japanese, the Italians, the Russians, and to some extent the Americans**. The British and the Germans were the world leaders in this department, and both could have leveraged that advantage better. Of course certain design struggles like with the British planned replacement for the Hurricane, the Typhoon, and the Germans planned replacement for the Stuka, the He 177, complicated this agenda. Design hell was a serious pitfall which could be difficult to perceive as it was happening.
* of course they did get the Ki-61 in time to make a difference but it was plagued with mechanical problems and was not really dominant over mid-war Allied types. The really good new Japanese fighters like the N1K1 and Ki-84 came about a year too late and in too small of numbers, and they too suffered from engine problems.
** The Americans eventually did produce effective and reliable radial "second gen" engines in the Pratt and Whitney R-1830 and R-2800 etc., but their inline engine industry, represented mainly by Allison, clearly suffered from a Strategic deficiency in altitude performance remedied only by the adoption of Rolls Royce two stage supercharger technology. The Allison did eventually work well with a turbo in the P-38 but this wasn't truly in working order until 1944 which is a year too late, though the P-38 still played an important role (despite many problems) in the Far East during the mid-war years.